Not surprising at all. It's become clear that what they've been doing with iOS all along is bootstrapping a new operating system. They started with Unix, not because Unix was optimal for what they wanted to do, but it's what they had and it worked well enough. Copland and Taligent and the rest failed because of Second-System Effect, which Apple was smart enough to avoid.

(As RMS wrote in 1983, "Unix is not my ideal system, but it is not too bad. The essential features of Unix seem to be good ones, and I think I can fill in what Unix lacks without spoiling them. And a system compatible with Unix would be convenient for many other people to adopt.")

Whereas such features as "background tasks" were simply a natural consequence of the architecture of Unix, Apple didn't expose that on iOS. Now they've finally gotten around to designing the background task subsystem they really want, and it's not just an emergent property of the generic Unix way. It's built for protecting battery life and privacy. It happens to be built on Unix processes (right?), but that's just an implementation detail for them.

They've been gradually deprecating Unix for 20 years, and designing the OS they want. iOS and its App Store allowed them to kill off large sections of the old interface at once. I fully expect inside of 5 years for all of Apple's operating systems to drop "UNIX" certification and become almost unrecognizable as "Unix". They've got enough market clout now that people will port Ruby/Python/Perl to a non-Unix macOS, just as they port them to Microsoft Windows.