Does the blues scale always have to strictly be a tonic followed by a minor 3rd followed by a perfect 4th followed by a diminished 5th followed by a perfect 5th followed by a minor 7th?
Scales tend to reflect reality. It's not that someone once came up with a theory from thin air. Notes that sound good together get put together in ascending/descending order to be called scales. To an extent it's what humans do. Then players can think along the lines of 'if I want that sound, I can use that set of notes and it'll largely work'.
The Blues scale reflects those notes used a lot in blues, obviously. Using the pentatonic notes plus one. However (there's often a however) - there are other notes which also get used a lot in blues. Thus, there is a minor blues scale, as you say, and also a major blues scale. And many times, players will flit from the notes in one to the notes in the other.There's also that microtonal factor, especially with 3rds and 5ths, which is difficult to write in normal Western musical language - playing 'in the cracks'.
So, yes, the minor blues is as you say - in A: A,C,D,Eb,E and G, but also the major blues. In A: A,B,C,C#,E,and F#. (The major blues uses notes from the relative major). Actually, by the time you've put all those notes together to make a 'full blues' scale, it's probably easier to state which notes from the chromatic scale AREN'T in there!