I’m not entirely sure what point you’re making. I agree, as long as a proprietary API like CUDA is cross platform it’s fine. But my nVidia GPUs also run OpenGL and OpenCL and Vulkan too.
Apple is forcing developers into adopting their Metal API and actively forcing other APIs off the platform, this is the real problem, Apple’s way or the highway! This is bad for the user because this means the developer has no choice but to target Metal and if they’re a cross platform developer it places a huge amount of extra burden on development. After Apple deprecated OpenGL and CL many smaller games Devs decided to stop Mac Games development. I saw one well known Mac developer say if Apple were so stupid to remove OpenGL from MacOS they move to the PC. How does this help the end user?
I know of one developer who has created software for real time performance and being forced to support Metal had him considering whether or not to continue with Mac support or drop Windows. He has struggled on and it has meant a huge delay in getting the latest version of his software out. The task is not easy for those with big development teams but for small developers it can be make or break. If it’s break then that has a direct affect on the end user.
Apple recently removed the loaner Mac from the Blender offices because Ton said they would never support Metal. Blender can’t support Metal because they don’t have any developers who know Metal and can support it long term. Instead they plan to move to Vulkan but Vulkan is only supported on the Mac via MoltenVK runtime library that sits on top of Metal. It’s not anywhere near 100% complete so Mac user may have less good performance or have visual limitations.
As long as it works users won’t care but the odds are stacked against it IMO. I’ve used Macs for a decade but recent developments have convinced me Apple is absolute poison for the professional. Use Macs at your own peril.