AMD keeps having issues because their drivers talk to the hardware directly so their drivers are massive bloated messes, famous for pages of auto-generated register definitions. Likely it's much more difficult to fix anything.
I'm asking because I think a firmware has to directly talk to hardware through lower HAL (hardware abstraction layer), while customer facing parts should be fairly isolated in the upper HAL. Some companies like to add direct HW acces to customer interface via more complex functions (often a recipe made out of lower HAL functions), which I always disliked. I prefer to isolate lower level functions and memory space from the user.
In any case, both Nvidia and AMD should have very similar FW capabilities. I don't know what I'm missing here.
Nvidia cards are much easier to program in the user mode driver. You cannot hang a Nvidia GPU with a bad memory access. You can hang the display engine with one though. At least when I was there.
You can hang an AMD GPU with a bad memory access. At least up to the Navi 3x.