It's not that it's never been discussed, but rather it's been brought up, we know about it, and there's not much to discuss because it's sort of basic lol. As you've said, it's super useful (as a Sheilda myself, I use it all the time!), but...it can't make a big enough impact on a match to warrant any in-depth discussion, other than the fact that some gimmicks with it...well...exist lol.
I could only see actual discussion on this if people came up with crazy implications that aren't already intuitive, like getting distance out of it to recover from further away (horizontally), or how using it in tandem with Sheik's up-B gives you plenty of invincibility against edge-guarders who aren't expecting it.
One thing I haven't considered/tested for differences is B-reversed instant transformations out of hitstun (when another Sheik/Zelda of the same color is on the screen), but I doubt that would yield anything that important, either.
EDIT: on another note...I think we're mistaken in considering the horizontal-momentum-transform thingy a B-reverse. I can B-reverse other characters' down-Bs, but I can't get transform to work, even with debug frame-by-frame inputs and 1/4 speed in training. iirc this is just downwards/horizontal momentum like the inputs for Diamond Dives, which is separate from B-reversing it lol.