The decision to add anti-cheat after 11 years is baffling. Not to mention that the anti-cheat runs on Linux, but Rockstar chose not to enable it. Store credit is really the only way Valve can give some remedy to this without taking huge losses.
Valve spent a long time telling gamers that GTA V is one of the top games for the Steam Deck, with Steam going so far as to add the game to the Steam Deck Verified list. After Rockstar added BattleEye anti-cheat, breaking Linux compatibility, Valve has not only removed the Verified title, it is also issuing refunds to gamers who purchased GTA V for their Steam Decks.