Yeah, the open drivers don't matter a whole lot. It just loads the closed source proprietary blob into the gpu. It's a step in the right direction but can be very misleading.
The worst part is when those blobs are signed, then you can't reverse engineer them and replace them with open firmware.
This is one of many ways by which NVIDIA actively sabotages the open source driver effort.
They were catching up at some point, and NVIDIA started doing that.
The good news is that with the new open Linux kernel drivers from NVIDIA, Nouveau folks will be able to use the same signed proprietary firmware as the proprietary userspace component of the NVIDIA drivers. So that should unblock development of the open userspace component of the libre Nouveau drivers too.
They do, IIRC, but, interestingly, Nvidia doesn't only because they put a RISC V processor on board that keeps it's own blob a few generations back (20xx?). I'm not sure that's actually more open, but I guess if you can run it with all open source drivers and no proprietary blob, that's good?
AMD’s linux-firmware blobs also exclude OpenCL support IIRC.
They do support OpenCL. You only need their closed source user space library libamdocl*.so and libamd_comgr.so to use it.