From what I can think of by the games standards, once the player learns the special ability the game instantly identifies them with greater expectations on their shoulders and will rate them more harshly if they perform the same way as they do without the SA

As a player learns a SA more things are expected from them and they are expected to influence the match more often, but from what I have seen throughout my time here is that performance and ratings also take into account how many times their SA got triggered during a match and are expected to change and influence a game, however playmakers literally don't do jack **** and the ratings sadly tumble on the MCs that have it cause they are expected to make that defence splitting pass.

As for the goals return though, that is a mystery... Could their performance actually worsen?!