That's not at all normal. Sandboxed Google Play doesn't consume more batter than privileged Google Play in a standard Google Mobiles Services device. It indicates something is very wrong with your setup.
13% Battery consumption is lower under stock Android
33% Can't tell the difference.
For users with a single profile with sandboxed Google Play installed before other apps, it should be very similar to the stock Pixel OS if you installed the dozens of Google apps they bundle on GrapheneOS and disable the various privileged apps they integrate which aren't usable on GrapheneOS. The stock OS drains more power with a typical simple setup because it has so much more installed and running. If you make it similar, it's nearly the same. If you use a more complex setup with multiple profiles and multiple push implementations on GrapheneOS, that's going to use more power. It still shouldn't drain nearly as much as you said above without something seriously wrong with the setup.
It's very easy to make battery life much worse. Using multiple push messaging implementations simultaneously is inefficient. As an example, using sandboxed Google Play in your Owner user, sandboxed Google Play in a work profile and a Private Space without it with various apps doing their own push would of course be far less efficient than a single Firebase Cloud Messaging push connection shared across the entire device. Having 2 installations of sandboxed Google Play you always keep running would be less efficient than privileged Google Play. Regular privileged Google Play shares the same processes and connections across profiles since it's built deeply into the OS and is implemented that way for efficiency like many OS services. If you compare having a single privileged Google Play vs. multiple sandboxed Google Play alongside apps doing their own push, of course privileged Google Play would be more efficient. You can use GrapheneOS with a similarly efficient setup and battery life will not be worse. You likely just have an inefficient setup. It can still be hard to narrow down what's really draining battery usage despite Android's battery stats getting much better over time.
To back up your survey with a reproducible experiment:
On my 6 pro, I got 2x advertised battery life until I installed one copy of Google Play services. Then I got advertised battery life.
It should be easy enough to uninstall Google’s stuff for a week and measure battery drain, then put it back.
Even with it though, I wasn’t losing 30% overnight. There’s probably some other problem. Maybe wipe + reinstall, then try with and without the 24/7 surveillance daemons?
I know, I had the problem when I got the Pixel. Already with the stock Android and then when installing Graphene. It took one or two weeks of tweaking until the battery life was on par with LineageOS. Not sure if I'd be able to reproduce it, but I think a combination of display settings and stand-by/background services. It's a thin line though, also making sure that Whatsapp notifications still work.
