The original intent for the A axis was for in-process gaging.
This was picutred in the brochure, but I do not think it was employed too often, if ever, especially in US.
This is the reason that the turrent will not index a full 360°.
I think if you're on T2000 and call T2900, it goes "the long way".
This was to prevent sensor cable twisting.
As far as using it to program or cut, I've never heard of anyone doing it, but it may well be possible.
Control the process, not the product!
Machining is more science than art, master the science and the artistry will be evident.