It's not AOSP but rather Pixels. Pixels are no longer support by AOSP. They went out of the way to no longer push any of the Pixel specific repositories or releases to AOSP. The impact is mainly that Pixels are now harder to support than a lot of other devices rather than easier. They'll sell far fewer Pixels over time because of these decisions.
I didn't know Pixel maintained its own kernel patches. And if there is a delay in providing that code to Pixel buyers, from my perspective, that looks like a violation of the GPL.
https://news.ycombinator.com/item?id=49369087