TLDR if under gameplay options you set difficulty from 'ACE' to 'STORY MODE' you get the campaign aim assist in multiplayer matches. Yes you read that correctly.
As discussed in this post:
https://www.reddit.com/r/StarWarsSquadrons/comments/js59jc/possible_bugneed_confirmation/
Indeed this has been tested by several players and under varying circumstances, it definitely does not work as intended. If you are running gameplay difficulty on ACE you are at a disadvantage in competitive games.
Either ACE gimbal aim assist is being applied above the intended VETERAN, or the aim assist is simply being passed through 1:1.
Special thanks to /u/Helequin13/ for discovering the issue
Special thanks to /u/Avenger__One/ and deathwatch for testing the issue and choosing to make it public. Even while giving up a potential competitive advantage, we can all agree it is better for the health of the community to have exploits like this known by all so that they can be fixed.
The bug on EA support site:
https://answers.ea.com/t5/Bug-Reports/ACE-gameplay-difficulty-is-applied-to-multiplayer-matches/m-p/9729354#M6279