I didn't mean to imply macOS and Linux had a substantial amount in common, as they're more distant cousins than close relatives.
While the two are no where near binary-compatible, the frameworks and libraries that go in to making WoW run under OSX can almost certainly be compiled across the divide, and I have a sneaking suspicion given that the launcher is QT and the API was originally OpenGL that a surprising amount of Linux compatible/native stuff sits under the hood of the OSX client.