The difference is money. Vulkan is an incredibly terse spec compared to dx12. You’d think that would make it much more consistent to work with, but really, it’s all it can do to keep up with msft and IHVs who pour money into coaxing AAA devs to use dx12. Then, even when the app gets something wrong and causes issues for end users, the IHV just makes a special case in the driver to correct it, because having a big important dx12 title run correctly on their hw is important to sell units.
Meanwhile, the same IHVs barely bother to support anything beyond the basic vulkan requirements, because it doesn’t gain them anything to do more. If a vulkan game experiences issues, IHVs don’t care because it won’t sell well anyway.
Yes, and the primary reason any of gaming on Linux is viable (steam deck, proton, etc) is due to Valve dumping money into it. AMD probably didn’t care about the miniscule number of chips they sold to Valve for the deck, valve just wanted a vendor who had the performance, and had decent Linux support.
But Valve is the one eating all the vulkan costs that msft normally eats on the dx side. To be clear, it’s never out of the kindness of their hearts, it’s purely because a msft dominated gaming ecosystem on PC is steam’s biggest weakness. They don’t want steam on windows to reach the point of EGS on the apple store.