Does it take less time to learn the fretboard when all strings are fourth apart, EADGCF, and then adjust your learning for the standard tuning of EADGBE ... vs... learning in standard tuning from the start?
If you learned to play a guitar tuned in all fourths you will not be learning the guitar fretboard. You will be learning how to play an instrument tuned in all fourths, or an alternate tuning of a guitar. Since your question says that the ultimate goal is to play in standard tuning, tuning in fourths will ultimately delay that goal. An instrument tuned in all fourths would be easier to learn to play from a melodic standpoint because of the consistency of intervals and patterns but this would not be helpful in the long run. First, playing simple open chords would be next to impossible and learning other types of chords would have to be either put on the back burner or completely re-learned once standard tuning is implemented. Second, any scale patterns across all 6 strings will also have to be re-learned, as well as playing intervals between the G and B or E strings. The major 3rd between the G and B strings does complicate things in many ways for guitarists but it also allows guitarists to do things that would not be possible on a 6 string instrument with all fourths tuning.
This question is not really answerable as asked. There aren't many individuals who first learned on an instrument tuned to all fourths and later learned to play on "standard" tuning as if it were an "alternate" tuning. If they existed and we had a way to survey a lot of them, we could compare the average time it takes to learn one way with the other.
Instead, think about a couple related questions:
- Why isn't standard guitar tuning uniform?
- Who does tune a 6-string instrument uniformly?
The short answer to 1. is that it is tied to a series of musical traditions where standard tuning makes for accessible fingerings on chords likely to be used.
One answer to 2. is [some] 6-string bass guitar players, who might use B-E-A-D-G-C. It does make for more uniform fingerings of scales across the whole neck. In bass guitar context, chords are much less common (and often limited to dyads).
Also, consider another 6-string (or more correctly, 6-course) instrument, the oud. In some traditions (e.g. Turkish), it is tuned in fourths, where it fits well with tuning systems that are essentially Pythagorean. In other traditions it may be tuned even more irregularly than standard guitar-- sometimes even in a reentrant tuning. In any case the tunings are chosen for musical reasons, not for ease of teaching or learning.
As one other answer has pointed out, there are guitarists using all fourths, and although I didn't watch all 50 minutes of video I do gather that these players are not (at their present stage of practice) learning standard tunes from books or the web. They're also using more complex chords than standard tuning was meant to support.
I would compare the idea to one of the most famous educational mistakes in modern history - the ITA [Initial Teaching Alphabet] reading system.
The idea was to standardise spellings, like tuning in all 4ths.
Great idea, until you then had to re-train everybody to spell properly.
I was fortunate to be just too old to have had to go through this, but I know people slightly younger than me who still cannot spell 50 years later.
See i.t.a: a great idea but a dismal failure for more background.
There are professional guitarists that use an "all 4ths" tuning, Tom Quayle being the example that came to mind. Tom Quayle uses EADGCF tuning, which is most frequently used between 4ths guitarists. An alternative is EbAbDbGbBE, tuning down the lower strings to match the higher, used by Ant Law.
The main benefit of 4ths tuning is that it improves improvisation and consistency between strings by maintaining the intervals. This would improve the ability to memorise and navigate the fretboard, and is beneficial for Jazz guitar especially.
It can however limit the amount of music you can play. Guitar music historically has been built around standard tuning primarily, so there will be a number of that you just won't be able to play using an alternate tuning, phrases from popular songs as well as the traditional open and barre chords. This may prevent you being able to perform certain music and styles in the future (as discussed in other answers).
Video Discussing 4ths Tuning in general, including some of the disadvantages.
Video discussing 4ths tuning with Ant Law.
I have never heard of anything like that - I would not be so arrogant to say it does not exist, but I am pretty sure there is no significant amount of non-subjective data points to look at regarding time to learning the fretboard.
I believe it is safe to say that all except for maybe an incredibly negligible amount of people have learned the fretboard with the regular style of tuning. Alternative tunings are usually a concept for advanced players, used for musical reasons, not as a tool for beginners to learn easier.
Using the standard tuning means you can pull from a plethora of resources on how to learn efficiently; you can learn all the regular chords and scale patterns "mechanically" (without even knowing what the absolute notes are) and work your way of knowing the actual notes. At the beginning everything is fresh anyways; there is some amount of just learning stuff by heart (i.e. the intervals or absolute names of the open strings).
Didactically, for me the most important thing is to have some sort of "mental anchor" (the open string) and then teach the pupil to learn to infer the rest from that. This works of course well with the hand at the basic position (index finger at 1st fret), which the average pupil is probably spending a lot in, in the first few weeks as finger/hand strength develops.
I would see no reason that this would be faster if the tuning were different. At the very beginning, there's more rote learning anyways; and in an intermediate state, when pupils can really "grok" the interval stuff, they will probably be used to the idiosyncrasies of the fretboard that it doesn't really matter.
Things get "worse" when not playing at 1st fret - as soon as you introduce moving the left hand around, everything is relative anyways. At this state, the intervals between strings don't really matter anymore - it is much more important to intuitively quickly "know" which note is on 8th fret of the D string without thinking too hard. And in the state that you still need to think about it you'll probably simply infer from 0th, 12th or maybe the popular 5th fret, and probably less often from the parallel fret on an adjacent string.
A six-string guitar tuned in fourths starting with E would be EADGCF, which would have six different string pitches. Adding a seventh string at the bottom would make it BEADGCF, which would be seven different pitches. By contrast, the present tuning uses a repeating pattern of five pitches, and even if one were to add a seventh string, BEADGBE would still only have five different string pitches. If one used a fanned-fret nine-string guitar to accommodate the wide range, GBEADGBEA would still only be five pitches.
The aspect of standard tuning which is slightly tricky is that while it uses a repeating pattern of five pitches tuned in fourths, the "seam" in the pattern occurs between the second and third strings from the top. If one recognizes the five-string pattern, however, I would think it easier to learn than a straight fourths pattern.