As Joruus just posted, you are still able to get all 48 minutes per position if you have filled out all starters, subs and reserves. I know that when an opponent just randomly forfeits a match, then you can't really do anything about it. Mostly you can see some signs before that someone is going to lose 50-0 to you, e.g. when they forfeited their last games or when they have sold most of their roster.