WHY WHY WHY do you do this to me game engine!? 
the official line is "Buzzerbeater does not encourage 48 min training/game since the training was not conceived to be handled this way"
i asked BB-Marin the other day what did the developers had in mind back then, since it was somewhat obvious that managers would adopt this strategy. he said he didn't know since he wasn't hired yet when the game was conceived.
i guess the developers thought that nobody would sacrifice their lineups for the sake of training and then train only 1 or 2 players as backups and using scrimmages to add up the missing minutes. they would have probably achieved that goal if they had set training mininums to 49 minutes instead of 48. when they set to exactly 48 minutes their plan went wrong and suddenly they had a basketball simulator where virtually every team plays with a center as PG (or vice-versa)