Seeing more and more thoughts be published like this in the last few months. It seems developer discontent might be growing with Apple.
Truth is, Apple is pretty good about open sourcing their stuff, especially when compared to their peers (Microsoft, Oracle). But that doesn't fit the "Google good, Apple bad" narrative that is popular in some circles.
It's important to remember that Android being "open" is googles attempt to commoditize a competitors product... you don't see google open sourcing core technologies related to source.