I don't believe what are you saying is happening every time.
Did you remember the old system of training, with the blue bar ?
When a player had his bar at 80-90%, you could make a lv1 or 2 training, in normal, and your player won 1 sp.
But for the next training, this blue bar was in the beginning (in 10-20%), so to fill it for the next sp, you should make a lv3 (practice match), in 3 bars, to get it (for a fast trainer).
We cannot see this blue bar with the new version, but I think it's still there.