And for macOS the OS itself provides enough system integrity that Riot don't need a kernel anticheat on macOS.
Steam Deck users need to ask Valve to similarly improve SteamOS's system integrity to prove to game companies that it's safe for people to run their games on it without compromising their game's integrity.
As a Steam Deck user I'd rather have the platform kept open like how it is now than lock it down. It's one of the significant advantages the Steam Deck (and PC gaming in general) has over consoles.