Apple's developer docs have been incomplete since the introduction of OS X. I don't expect it to get any better before hell freezes over. The article mentions that this makes it hard for newbies to learn. That's true but my guess is that by the time those chickens come home to roost, JavaScript will be called a systems programming language.
I wouldn’t put it quite as strongly as that, but yes, the OS X docs have never been great.
It’s a shame, because the classic MacOS docs were amazing, amongst the best technical docs of all time at their peak. (I had a shelf of Inside Mac books, and they were useful for years.)
Trying to learn Cocoa dev in 2019 is very frustrating.
Not only there are practically no updated resources available (books, courses, etc), but the Apple docs are really lackluster.
At first I thought Catalyst was about empowering Cocoa devs to bring Mac apps into iOS, but now I see it's just the opposite. I imagine the number of macOS devs has been slowly shrinking over the years.
Edit: Updated wording to article's title change.