FWIW, my experience with blowout minutes is that you can get 48 minutes for your trainees if the following conditions are met:
1) Dress no more than 9 players - your trainee, and Starter + Backup/Reserve for the other 4 positions.
2) Set the trainee as Starter + Backup + Reserve at the desired position
3) Set to Strictly Follow Depth Chart
4) Ensure the trainee has decent stamina. If the trainee is 4 (inept) or lower stamina, there's a chance the coach will decide the trainee is tired enough he should come out of a blowout, even in SFDC. I assume it's because there's a higher injury risk when a player is tired or something, so the coach is weighing that against what you told him to do and figuring it's better to ask forgiveness for pulling the player.