Android 17 QPR1 is the first release since Android Honeycomb (3.x) adding new APIs for app developers without a release to the Android Open Source Project. The new APIs are currently exclusive to the Pixel OS and aren't available to other Android OEMs.
https://developer.android.com/sdk/api_diff/37.1/changes
Possible? Yes. Plausible? No, mainly due to the massive ecosystem that Google has built and the fact that maintaining compatibility with newer versions of Android without actually rebasing on top of that newer Android version would be an insane amount of work.
is it possible or plausible for grapheneos to just simply fork android officially and break control from google?
It’s entirely possible but would require a massive increase in volunteer manpower just to keep up.
In a way they already do. The trouble is that most big companies want the Google name and PlayStore.
GrapheneOS soft forks Android. I think they’re taking about a hard fork.
Possible? Yes. Plausible? No, mainly due to the massive ecosystem that Google has built and the fact that maintaining compatibility with newer versions of Android without actually rebasing on top of that newer Android version would be an insane amount of work.