It seems to me that the discussion of rehearsal and methods for improving ones performing skills is crucial in the development of a magician. Yet this section of the forum only has a few entries, while the card section, for example, has thousands of threads.

Hypothesis: If magicians spent more time in this forum (and by that I also mean contemplating the subject and working on their skills in this area) then in sections that focus on sleights, we would see a major jump in the quality of the average performance.

Any thoughts? Empirical evidence for or against?

I agree. In fact this is the first time I have been to this section myself! And yes the numbers are shocking! Well I propose that too many cooks may spoil the broth and perhaps a small number of dedicated posters means more breathing room for all.
As for your hypothesis, I think if we all spent less time on magic forums and more time with (sponge) balls in hand or whatever we would be better off, but then we wouldnt get to parade our greatness around for all to see, don't forget how BORING it is to sit all by your lonesome doing the same thing over and over again, better to get the gimmicked version.
I simply think that a lot of people stay away from this section because they don't want to admit how little they really practice...you don't need to practice much if you never perform!