The very argument that was presented when iOS first came out, as well as whenever touchscreens on MacBooks come up, is that the UX is fundamentally different.
So why would it suddenly be a good idea to import this from iOS?
Perhaps the people against touchscreen on MacOS finally retired or gave up the fight, so Apple is slowly preparing what Microsoft did years ago with Windows 8.
What Microsoft did, and still hasn’t finished. System preferences still contain massive amount of details contained in Windows 7 (and older!) style windows.
At least Apple managed to move all their settings from one paradigm to the next in one year. I’m looking forward to the improvements they make to the app in the future.
They didn't finish it because they went hard, all in one go, and suffered consumer backlash as a result. From this Apple learned that you have to boil the frog slowly.