Why?
Why not? It would allow to have better GL in Wine than what the host GL supports. On macOS for instance, but also other platforms that may only have vulkan.
That's a reason to use zink at all, not a reason to have PE zink in Wine. Why do we need the latter? The only reason I could see is to avoid doing any of the work of thunking GL to Vulkan, but I think we're quite a lnog way off from being able to drop support for host GL, at least on platforms other than Mac.
Why does it mean that?
Because that's how it works on Windows and that's how Mesa is implemented. Its wgl implementation is limited to what an ICD is supposed to do.
Uh, what? Last I was aware, Zink on Windows built an opengl32.dll. Is that no longer the case?
It also makes supporting it as an optional feature easy, and matches native behavior too, which dynamically loads an ICD depending on GPU settings.
Supporting Zink as an optional feature seems also easy if it were opengl32.dll...? -- https://gitlab.winehq.org/wine/wine/-/merge_requests/11161#note_143711