C++: wlroots claims it can't support the x11 backend when using nvidia drivers. But why?

I'll start this stream with actually using the environment variable added to libcwd in the previous stream. Then I'm going to look into wlroots in the hope to understand what it is trying to do exact; once I understand what it is TRYING to do (and failing) I can't imagine that I can't make it work on my box: after all, I can totally fine open a window using xcb and draw into it using my vulkan engine, so surely it must be possible to use that as "x11 backend" for the drawing being done by a wayland compositor?!