Not sure I'd call myself a fan, but I was an engineer on the Xcode team for a decade. The answer to your question about coupling is "ease of testing and coheren

Not sure I'd call myself a fan, but I was an engineer on the Xcode team for a decade. The answer to your question about coupling is "ease of testing and coherence". Prior to Apple, I was a senior engineer on the dev tools team at Microsoft. We did the same exact thing wrt full-release testing and vendor hardware. I'm not saying I agree with the way either company handles coupling, lock-in, etc. but if you don't think that the Windows UI is coupled to ring-0 you don't understand how it works.