It’s a good first step imo. It maintains compatibility with Google apps, which as the author notes, would be needed for it to not be a dead project. It’s a pretty good balance.
That said, I’m not familiar with Graphene, so I could just be wrong.
Dont know how this should help "maintaining compatibility with Google apps". Has no impact here. GrapheneOS does that by shipping normal play store and services, but with a compatibility layer to be able to run in a sandbox