Earlier quoted context omitted.
FYI, firefox is working on switching to rendering the entire page in opengl which should bring it's motion mark score up substantially. Details on that (and how to enable it in nightly at the bottom of each post) at https://mozillagfx.wordpress.com
They’d better switch to using metal because Apple deprecated OpenGL for MacOS.
So Metal-only isn't really an option for many projects, it's OpenGL + Metal or just OpenGL (for now).