Looks like today's update on their Android Github page is better. NO battery drain yet
Quoting this for other #GrapheneOS users, if you have battery drain then it's probably because you have Signal.
https://github.com/signalapp/Signal-Android/issues/13704
The hardened signal fork Molly is far more optimized and doesn't have this issue. A pull request was made to Signal to fix but they never merged it. Been ignored.
Discussion
The PR I mentioned is still open, if it comes back then the attached is probably the reason