I thought SDL3 covers everything on that front though? Don't think we need to reinvent the wheel too much for window management.

...and GLFW, winit, RayLib, SFML, sokol_app.h etc etc... ;)

It just offloads all the pain and hassle to the SDL maintainers. Also SDL is a pretty big beast (partly because it needs to accumulate a lot of hacks and workaround for buggy drivers and window systems). It would be nice when all those accumulated hacks wouldn't be needed in the first place.

For the idea of portable gfx applications in WASI it's also not really an option to base the window system glue standard on SDL (I guess though that SDL could be the base for one specific implementation of the WASI window system glue interface).