So, the trainer with career extension specialty might stop (25% chance since there's the usual random factor) the drop for older players and if ever there's a skill drop, the trainer level will minimize the drop (for illustriation purposes: instead of 10.0 going to 9.0, the new skill level might be 9.1 for lower level trainers or 9.2 for higher level trainers)
I had thought so too....if I could find the link where they explained it.... but yea, I learned awhile ago, trainer level reduces amount of drop.