Nope, I tried that a couple weeks ago.
I've done
PG
starter: P1
backup: P2
reserve: P2
SG
starter: P2
backup: P1
reserve: P1
and I still got 43 minutes for each player.
What I haven't done yet is:
PG
starter: P1
backup: P1
reserve: P1
SG
starter: P2
backup: P1
reserve: P1
but I'm not sure what that would do, and P2 will have his training cut.
I have yet another walkover game this season (unfortunately because of this active manager intentionally creating walkovers) so if you try something that does work, I would love to know. (I use 2 position training)