https://www.androidauthority.com/google-not-killing-aosp-3566882/
I think reading this article it's clear G didn't make an 'oopsie' and perhaps still will share device trees, kernel commit history and driver binaries for pixels. They unfortunatly won't.
This probably means it won't be impossible for GrapheneOS moving forward, but wil make it significantly harder and time consuming, especially with the same resources as they had before.
I'm positive they can pull the port to A16 off, though i'm not sure this will be sustainable going forward with the situation as is. Especially to support newer upcoming pixels.
Therefore i sincerely hope they still will get OEM access one way or another in the future, or the community steps up with donations, so they can expand the team for the massive extra amount of work that is necessary as of now to reverse engineer.