That's good to know and something I had not noticed occurring with sufficient regularity to chalk it up to anything more than a training bonus; certainly nothing I'd count on--again, the reason for the mystery is lost on me, but apparently others enjoy it.
When I play a simulation, I'm not looking for simple (complex is good) just something that makes sense; the settings for training don't allow you to train IS for a guard without playing him out of position. There is nothing straight-forward about getting pops at IS when training 1on1. I have no problem with that occurring but it is no different than the random pops people are complaining about here. You should be able to train a player at the position you decide to play him at without guessing about settings. That results vary based on player coding, trainer ability, fatigue, etc. are understandable and that is where the variation should occur.