Hi, just now looking up this issue.
I bought the Palace Edition on Steam and also have the EA Play subscription thanks to Game Pass Ultimate, and I even had the M3 GTR at one point (just to clarify, the cars DO GET GRANTED, but the Palace Edition cars are the ones that need to be purchased), but it's been months and I can't get the new EA Play rewards nor I can get my M3 GTR back, as the game doesn't recognize my subscription to the service.
Also, the game launching through the EA App should recognize the subscription and I am not willing to spend more money to subscribe again through Steam because I already have the subscription and even the launcher says I do.