haven't read anything in particular about that subject. =( I wouldn't *think* so as it allows teams to experiment offense and defense ideas that would be considered highly risky in season games.
I asked my Gm in USA AA#1 to put my TE in a backup RB slot for a game... just to see how it would pan out. He signed off on the idea with no hesitation. Sadly, our running game was slammed that game so it didn't give much information. Previous game he was the starter FB with no backup, and I was happy to see that my TE did well.