You’re pretty misinformed here. EA (or rather the internal studio, Respawn) had to include the EasyAnticheat .so file (which is specifically designed to allow EasyAnticheat to function under Linux – .so files are the Linux equivalent of Windows .dlls) in their Apex Legends builds to begin with. Otherwise, EAC will not run on Linux, period. This developer opted-in to EasyAnticheat running, and has continued to opt-in to this.
This isn’t Valve “tacking on” support, the presence of that file is an explicit “we’re permitting this to work” (even if they don’t “officially” consider it supported).