1e2j6 GrapheneOS doesn't root your phone at any point. What you're most likely referring to is SafetyNet / Play Integrity API which apps can use to disallow people from using an app on a non-Google certified device.
This doesn't seem to be the case with this game, as I had someone who owns that game look at it, and it works fine for them on GrapheneOS, albeit on a Pixel 6.
That led me to think that the game might be 32bit, and Pixel 7 devices are incompatible with that, but they've confirmed the game is 64bit.
Is the game on your owner profile? In that case, we can try something.
- Create a new user profile.
- Install Sandboxed Google Play on the second profile.
- Go back to the owner profile, Settings > System > Multiple Users > Find the new profile > Install Available Apps" and toggle on this game.
- Go to the new profile once again, log into Play Store and see if you can update it on the secondary profile. Do make sure that Play Store has the OBB toggle enabled, of course.