Even if their claims are accurate, it usually has the asterisk of *Only with Apple Metal 2. I honestly cannot understand why Apple decided they needed to write their own graphics API when the rest of the world is working hard to get away from the biggest proprietary graphics API.

Because vendor lock-in and full control over their APIs which has always been an apple staple but especially now.

5-10 years ago they were still serious about open standards, like OpenCL.. Now it's all locked in.

I'd like to note that Microsoft is doing no better with DirectX. If it weren't for the drivers on Windows being distributed and supported by the GPU manufacturers themselves, Vulkan would only be a thing for Linux (incl. Android) and custom niche devices now.

Because when they wrote the API no real standard existed to suit their needs.

Yes, and instead of writing an open standard or adapting Vulkan when it came around, they instead decided to double down on proprietary and moved to Metal 2.

I mean, Metal is a good API and they designed it first. They could've decided to abandon it when Vulkan came out, but I guess they just didn't want to make their API worse. Not ideal, yes, but I don't really blame them for the decision.