7 seasons ago I trained my 2 wide midfielders with SAs. 1 as a dribbler, the other with the super shot thing. I have been most unimpressed. Both players are still starters, but I have to say I expected more from their special abilities.
Recently trained a MC with free kick SA and he puts more into the wall, wide or into the car park than he gets on target. Would at least expect him to force the opposition keeper to work.
So I'd agree that SA training seems to make little to no difference.
I'll only use it in future to put the brakes on players I want to appear on next seasons negotiations lists.