None of the videos on youtube are is concert pitch.
These days many musicians who play Baroque music such as Bach tune their instruments down to the lower pitch of A=415, which is exactly one half-step below the modern standard of A=440.
It is generally accepted by modern performers of early music in the historically-informed style that A=415 was the tuning that Bach himself used for the string pieces he composed.
I'm quite sure that many examples you can find on YouTube are of a musician playing in A=415; furthermore, such a musician would be playing a specially-designed Baroque cello with period-correct strings made of sheep gut, not modern strings made of steel. Such a "baroque" cello would be designed, braced and set up differently than a modern cello, and would use a different kind of bow as well, and would be played in a different style -- for one thing, using a great deal less vibrato than "modern" cello players use. A Baroque cello with sheep-gut strings has a different sound than a "modern" cello. It is not as loud and cutting, but it has a character of sound that early music fans love.
The whole point of historically-informed performance is to try to use modern scholarship to go back to the sounds, instruments, and playing techniques that, to the best of our knowledge, were used by Bach himself, in contrast to playing on a modern instrument with modern strings and modern playing technique.
All this notwithstanding, if you want to learn to play Bach, you should tune your modern cello to A=440 and play it in the modern fashion with your modern bow. That is what your particular cello was designed and built to handle, and it's perfectly correct to play your instrument in that fashion.
I know many professionals (mostly college professors) who own both a Baroque cello and a "modern" cello, and a variety of different bows built after the design of different historical periods (I know people who have six different kinds of bows!) and use one cello or the other depending on the orchestra they are performing with and the type of music being performed. These people, however, are deeply committed to early music; extra cellos and bows are very expensive.
There might be a second question here, which regards the internal tuning of the cello strings, relative to itself. Cellos are typically tuned in fifths (C-G-D-A) of course, but there are pieces that require a different tuning (a technique called scordatura). In this case, wikipedia mentions that Bach's 5th Cello Suite was written for a scordatura in which the A string was tuned down to G. However, no such mention is made of a similar technique being used in Suite No. 2, so I assume it is written for standard tuning.
I don't know if this was your question, but I figured it was at least worth mentioning the issue.
As MarkM pointed out, your claim is unsubstantiated. Consider further that "concert pitch" is not a fixed value. In the Good Old Days of Yesteryear, middle-A could be anything from 409Hz on up ( Wikipedia).
Whether any particular YouTube recording was pitch-shifted in postprocessing is unknown.
Maybe you could point out which videos you're listening to. Period tuning is sometimes lower than A 440, but from a random sample of top results in youtube I found:
Mischa Maisky :Mstislav Rostropovich:
Both squarely in D minor and A440 as I would expect.
Concert pitch depends on the orchestra. My instructor tunes to 441, as do I. It also depends on the acoustics of the hall and the atmosphere. So, many orchestras tune between 440 and 445 or 6. I noticed that some European orchestras are tuned to 445. NY orchestras to 442 or 443. Boston to 442. West Coast to 441 or 2. Right now, I'm tuning to 441 for the Bach Cello Suites.
Here's a thread on the topic. Why are orchestras tuned differently?
I play the second suite with normal 440 pitch, and it sounds fine to me. In the fifth suite, I'm pretty sure you're meant to tune your C-string down to a D so that you can get the bottom note, but that's not what you were asking.