VK_KHX_external_memory_capabilities missing on GTX 780 Ti

I only see the VK_NV_external_memory_capabilities

Searched out on this forum and found vulkaninfo from GTX 760 that had the KHX extension as well.

There’s software that requires the VK_KHX extension. I’m unable to start it because the KHX extension is not present.

I know this extension is already KHR and it’s going to be available in the next driver release, but why do I have this problem in the first place?