I agree with this, I've stated before (and been shot down) that I believe the training equation is more likely the following:
(Minutes played/48) squared
This means a player who played 36 minutes at a trained position would recieve approxametly 56% of the training. This seems much closer to what has happened with my secondary trainee (my third trainee). He has often received 36-44 minutes of training and does not seem to be falling too far behind the training simulator spreadsheet (I think it was made by Joseph Ka).