This is a very inaccurate summary of the space. There aren't that many studios doing Vulkan ports, unless you want to target Linux, but even Valve prefers Proton and are telling people not to port. Or Android/Stadia, but nobody gives a shit about that to do that.
The big engines have support for both Vulkan and D3D12, and use the D3D12 backend on Windows.
Studios are porting to D3D12, by comparison, somewhat because of Xbox, but also because it's a somewhat standard upgrade from D3D11. The developer experience of the D3D12 debug layer is much better than Vulkan.
Disclaimer: I lead the Vulkan and D3D12 ports of the engine at the last game studio I worked at.
The big engines have support for both Vulkan and D3D12, and use the D3D12 backend on Windows.
Studios are porting to D3D12, by comparison, somewhat because of Xbox, but also because it's a somewhat standard upgrade from D3D11. The developer experience of the D3D12 debug layer is much better than Vulkan.
Disclaimer: I lead the Vulkan and D3D12 ports of the engine at the last game studio I worked at.