https://bugs.winehq.org/show_bug.cgi?id=41166
--- Comment #13 from Sveinar Søpler cybermax@dexter.no --- Most likely related:
https://us.battle.net/forums/en/wow/topic/20758847141?page=5#post-81
The OpenGL backend for Mac, and some bugs. https://us.battle.net/forums/en/wow/topic/20758687941?page=2#post-32
Not sure, but "missing ground effects" is also a problem in DX9. Windows users can switch to DX11, so its "solved" that way, but Mac users that could not run Metal had this problem. OpenGL for Windows on the other hand might not be working the same in the client as for Mac's i guess.
This was from september/october, but OpenGL is still borked when running under Wine... so what i think happened with OpenGL support is that some coder (as the previous posts indicate) opened up this option "over the weekend" for windows a long long while ago, since it was already in the client. Then OpenGL was updated for Mac's, and that broke it for Windows/wine users. I remember OpenGL was somewhat bugged with texture flickering and stuff last expansion too, so its a good while ago since wine were able to run OpenGL under wow.