Minutes are minutes, nothing more. As others have stated time after time, the needed minutes is 48+. This means that regardless of type of training, be it 1-position or 2-position training, the objective is to get the player to achieve 48+ minutes overall for the week in said position(s). For example, if doing 1-position training for your Bigs, the trainee needs to achieve 48 minutes at Center only. If doing 2-position training for your Bigs, then the trainee needs to achieve a combined 48+ minutes at Center and/or Power Forward. So despite your thinking, having the trainee play 48 at Center and 48 at Power Forward, only 48 minutes of those 96 that he's played will count towards his training. You are only doing 2 things when you have him play 48 at both positions. First, his gameshape next week will be horrible and, second, you're wasting valuable training minutes that could be used toward another player in his position.