I'll post the link again since you apparently
DID NOT read it:
https://blogs.unity3d.com/2016/06/17/wwdc-unity-metal-tessellation-demo/
Apparently, Metal supports compute shaders. Now, the ball is in Frontier's backyard.
It's not that black & white. "Metal supports compute shaders in some unspecified manner" isn't the same as "Metal supports compute shaders in a way that gives acceptable results in a specific project".... that's why I said in the very paragraph you picked out:
....If Metal really doesn't properly support some of the functionality available in current OpenGL standards....
and in the following post said:
Frontiers support article regarding Horizons that got linked earlier mentions Metal also doesn't support compute Shaders in the way needed to make it viable, which is why they weren't able to do so.
Does seem they looked into it, but then found it wasn't a practical option.
There's absolutely no point linking Unity3D blogs and going "Well Unity has support so some developers can come up with a use for it in their projects, so Frontier can".
Software doesn't work that way. Especially when you have a engine developed to target one situation as that's how it was at the time, and then a company goes and buggers about further, cuts supporting what they had supported and the whole situation ends up making continued support more of a headache to approach in a practical manner for existing software.
That's why I didn't bother to read your link in relation to if it's viable for Frontier to utilise, as it doesn't really contribute anything at all to Elite Dangerous and what is and isn't practical.