Not fully what you're asking but this was posted on their official Reddit

Google has already had to change how they plan on implementing their blocking app installs from unregistered developers after a lot of backlash. "Sideloading" will still be possible, as we've all learned from recent news. The 24 hour wait does add some friction to the whole process, which is the point of course, but it's far less bad than some people are trying to make it seem. 24 hours, then it's over and the user is free to install apps as they please.

This "sideloading" restriction is not even the biggest problem right now. Play Integrity is worse and does affect us directly. The effects of Play Integrity are showing up in multiple places, like now apps can't be installed via Play Store, maybe Aurora in the future, apps refuse to run, Play Integrity verdicts are worse if an app was installed via another source than Play Store, and Automatic Protection has Play Integrity features being added. It's a far bigger problem. It causes enough friction for some users that they give up on GrapheneOS or other non-GMS OSes to go back to whatever stock OS they had before, one complete with Google apps with privileged access and awful privacy. This other issue just got a lot more attention, and I'm guessing because it's easier for people to fully understand.

We have been in touch with EU regulators about Play Integrity and I hope that can continue in the future. Google isn't going to change things because a small group of people are complaining. We need regulators to help with big issues. We need to find a way to make them understand what is happening. Play Integrity is a big example of them locking things down under the guise of "security." Fixating on other smaller issues is, in my opinion, less effective and a waste of time and resources. The "sideloading" thing has enough attention and opponents to the change have had some success.

I can't find the post, but I recall the Graphene developers saying this would not affect GrapheneOS because of the way they have play implemented. Play services on GrapheneOS is sandboxed, it does not have permission to enforce this check.

well for one, you don't even need play services for all apps downloaded from the play store. and for another, even for the ones that do need it, play services run as an unprivileged sandboxed app, the same as any. so it can't enforce anything google wants because it has zero control over anything.

Hey, honestly I don't know much about GrapheneOS. I only know it's available for Google Pixels. But you're right. All Google-certified devices will be 'locked down!'

You do not need to install Play services on Graphene. You can. You can also install MicroG, or you can skip both and use NextPush or ntfy.