according to this topic: Windowed Mode - resizing quits WoW - #71 by Tholaren-nordrassil
Blizzard changed some backend WoW code with 9.2, and now it’s highly unstable in MacOS (and it’s absolutely unusable in Windowed mode). Blizz says “not our fault, it’s a bug with macOS”, even though literally NO other games or even applications bug out like WoW does. And now they’re refusing to fix this, or revert their code to the version that worked flawlessly.
Thanks, Blizz 