One of the visible impacts of MVC is that changes occur in real-time: you modify a value in a dialog, and everything affected by that value instantly updates. This is already common in Mac apps (in contrast to Windows apps, which typically want you to press “ok” or “apply”), so it wouldn’t surprise me if Apple was already using a modern MVC variant. It’s a well-known pattern.

https://developer.apple.com/library/archive/documentation/Ge...

Elsewhere, the documentation contrasts the Cocoa and Smalltalk versions of MVC where all three pieces communicate directly:

https://developer.apple.com/library/archive/documentation/Co...

Like you said, this separation means you can "drive" the same model through different UIs. That's one of the things I always thought was cool about AppleScript support -- the app exposes a different interface to the same model.

The harder problem is building accessibility API's for oblivious developers, so they can retrofit at the last minute before release (as usually happens). Apple's done a pretty good job there, harvesting the semantics of existing visual UI's to adapt for voice/hearing.