Wine is a fully open implementation of Windows APIs on Linux. The game cannot assume that the API's behavior is fixed on WINE because anyone can change any of t

Wine is a fully open implementation of Windows APIs on Linux. The game cannot assume that the API's behavior is fixed on WINE because anyone can change any of the functions to do something unexpected with a quick patch. One example may be hacking up the DirectX implementation to draw some objects as transparent rather than opaque. 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.