"Subset" is not the right word here. Vulkan has pointers now, but (as was discussed in a recent thread), there are serious limitations compared with "real" C++. At the same time, Metal has its own limitations, not least of which it's lacking acquire/release semantics on atomics and a device-scoped barrier.

OpenCL is a little strange because older variants don't have advanced atomics (or subgroups), but does have pointers. I'd be curious to know what specific thing is not available on DX12 and Metal but missing in Vulkan, especially because I'm not aware of any DX12 feature on the critical path for OpenCL that's missing from Vulkan (at least as an extension).