I have been a ROBLOX player since 2009. The Linux anti-cheat began to be enforced because practically no-one used the Wine port for honest gameplay; it was almost always to do some kind of memory manipulation or for script kiddies to execute exploits.
Not many people outside of the ecosystem are aware but ROBLOX was actually really late to the concept of dividing client and server responsibilities. It used to be that one client could actually propagate changes out to all the others; therefore if you could manipulate memory you could arbitrarily execute code (within the sandbox) on all other players. There used to be popular scripts like Person299's admin commands that could be injected into any server and allow the exploiter the ability to run chat commands like "kill/<user>" or "ban/<user>" (self explanatory). Only a few years ago did they introduce RemoteEvents and ServerScriptService which finally allowed developers to ensure some code could only execute server side, and properties like FilteringEnabled which blocked clients from propagating local game changes out to the server and everyone else. This broke hundreds of thousands of old games, which was probably why they held off, but nowadays any new games are using these new features to prevent easy exploitation like in the past.
My guess is they have nothing against Linux now, because they have implemented proper security, but the only thing stopping them are the technical challenges, and there are not enough people in their target demographic who use Linux to make porting worthwhile.
Not many people outside of the ecosystem are aware but ROBLOX was actually really late to the concept of dividing client and server responsibilities. It used to be that one client could actually propagate changes out to all the others; therefore if you could manipulate memory you could arbitrarily execute code (within the sandbox) on all other players. There used to be popular scripts like Person299's admin commands that could be injected into any server and allow the exploiter the ability to run chat commands like "kill/<user>" or "ban/<user>" (self explanatory). Only a few years ago did they introduce RemoteEvents and ServerScriptService which finally allowed developers to ensure some code could only execute server side, and properties like FilteringEnabled which blocked clients from propagating local game changes out to the server and everyone else. This broke hundreds of thousands of old games, which was probably why they held off, but nowadays any new games are using these new features to prevent easy exploitation like in the past.
My guess is they have nothing against Linux now, because they have implemented proper security, but the only thing stopping them are the technical challenges, and there are not enough people in their target demographic who use Linux to make porting worthwhile.