Did people actually claim that? I don’t remember it but I don’t follow Vulkan and would stop reading subthreads when they turned towards “Apple should just use Vulkan”.
If Vulkan was designed to be vendor neutral (it was) it seems very unlikely it would be unimplementable by Apple if they wanted.
Previously: https://news.ycombinator.com/item?id=42021237 Linux on Apple Silicon with Alyssa Rosenzweig