While I concede documentation has slipped greatly the last 20 years to an all time low, Apple did produced the Inside Macintosh series, possibly the greatest developer documentation ever written.
I spent a lot of time in the IAC book many moons ago, extracting the concepts and motivations left unspoken in Apple’s newer “long lists of buttons” documentation. “How” stuff makes vastly more sense once you understand the “Why” that underpins it all.