The post is in the link, the article with more background info is here (it cites the mastodon post): https://www.androidauthority.com/custom-roms-vs-google-3469378/
I originally saw the article on this post on [email protected] and went looking for links.
This is a great reason to support GOS with donations https://grapheneos.org/donate
Suing google for fair and open API access will not be a cheap prospect. I hope the current anti-trust litigation makes them less monopolistic