Apple is using Metal because it's a modest improvement over OpenGL (in some areas; it's a regression in others) and, more importantly, their OpenGL implementation is extremely buggy.

You haven't said anything about Vulkan vs. Metal, and you can't, because Vulkan is a better API for the reasons I described upthread.

I can't say anything good about Vulkan, because I am not going to buy a new laptop or a Google Pixel just to try it out.

Then please stop saying it's a bad API.

Full disclosure: I have colleagues and friends on the Khronos standards group, and I don't like seeing their work bashed without specific technical reasons.

Where have I said it is a bad API?

I have said it has insignificant market share and that share won't get better outside GNU/Linux for the foreseeable future.

That has nothing to do with quality.