It always confuses me a bit when people say "IDPA is not training."
It may not be (ok, it isn't) formal training, with an instructor helping improve techniques, awareness, etc. It isn't FOF training, as the targets don't shoot back.
But it is practice, and trigger time; and more importantly it's practice that gives immediate feedback with regard to one's ability to hit what one aims at, quickly.
So, it can be training, depending on whether one tries to learn anything from it.
In that sense, everything is training. (Then again, I practice opening doors and starting my chainsaw by rotating my center, not flexing or extending my arm - when feasible - to train at applying body mass in mundane applications. Does wonders for applying that force on the mat...)
Edit: How this relates to the OP's question - I would use my carry platform (or similar) to maximize my trigger time under some degree of stress with the weapon; I'm not that worried about winning (and frankly, I'm a long way from winning at my club; I'm not that fast - though I usually take 1st or 2nd for total accuracy) but am more concerned with being effective with my carry weapon(s).
I have used match results to compare my different platforms, and see which I shoot best in a variety of conditions. So I guess I view IDPA as either practice, or pre-season, depending on how you look at it.