[1] e.g., https://en.m.wikipedia.org/wiki/NProtect_GameGuard
Of course, it's possible (if much harder) to go in and hack up the DLLs on Windows. Anti-cheat addresses that by whitelisting known-good MS hashes and/or requiring some type of signing. There's a lot more overhead involved in doing something like that for WINE, since every distro's build would be different, it's common for users to have their own builds with game-specific patches enabled, etc.
I've been out of the WINE scene for a while, but I'll say that I don't believe many WINE users are trying to exploit the platform to cheat. I think it's purely a cost-benefit tradeoff. The vendor doesn't feel supporting a legitimate WINE use case is worth the expense of figuring out a reasonable way to validate behavior, handle integration with distro builds, support debugging/custom patchsets, etc.
I would imagine Wine is in a similar predicament.
It seems far more likely to that most players are just using Wine for its intended purpose—to play Fortnite on Linux.