If adding a capability to boot another OS is seen as a big gesture, Google providing an entire operating system source code should be a bigger deal yes?
One is cracking open a door (Apple) and the other is opening the door wide, and welcoming you into your home.
Google doesn't provide "entire operating system source code", it provides some parts, while other they keep closed. Also they are continuously removing parts that are essential from AOSP (that are either open or closed).
Removing support for Pixel devices makes AOSP even less useful for developers, because belief that VM will be a good replacement for real hardware test environment is a fairy tale next to sleeping beauty.
So no, they don't provide "entire operating system source code", what they provide is a caricature of open source project. So maybe they should call it COSP.
Didn't mean to imply that Aapl can't be accused of perfidious behaviour on the sw side, but the erstwhile welcomes mean that Goog's betrayal, when it happens, even a minor one that doesn't kill the biz, hurts a lot more?
One is cracking open a door (Apple) and the other is opening the door wide, and welcoming you into your home.