That must just be a miss understanding it’s never been that way. All of that intermetate stage occurs outside the kernel driver in userland…
Probably the confusion comes from the kernel driver for AMD can be talked to by the blob or Mesa… the entire compiler is always in userland though regardless, the only thing the kernel driver ever sees is a binary GPU programs and data.
The complexity of GPU drivers is something that should not be just reinvented … becuase you end up being 10 years out of date before anyone gets time to work on it. So any time Haiku can just add the APIs and adapt it’s expectations to what the existing drivers provide… its a win, it won’t be perfect but it can work. And code that works is the best kind. Another upside is most of the graphics subsystem in Linux is dual licensed MIT.