Please.
I do not condone or endorse illegal activity. That does not mean your use of GrapheneOS might not be used against you if you use it at an inopportune time. There is currently almost no discussion online about this, so it’s worth a mention.
Edit: I forgot to mention some obvious context in my head. Think journalist, in Russia, using GrapheneOS for “safety.” In such a situation, probably a terrible idea.
A mention, not a core argument against use.
In my reading, your core point is an old argument: https://en.wikipedia.org/wiki/Nothing_to_hide_argument
"You're painting your fence beige instead of white? Are you sure that's a good idea? What if there's a crime committed in the neighborhood - beige-fenced deviants are the first that the police will look at!"
GrapheneOS is likely not a secure system, but neither is any smartphone OS. I'll compliment anyone taking steps towards transparency that makes governments and global-scale corporations tremble at the knees.
It actually put a little fear in me because I look around and not a lot of internet users in my small hell hole of an open prison I call home and i was like "dude. You're like a alert beacon screaming here is a tor user, check him out".
I was using tor at the time and that is the last day I used it because this use case fit me somewhat. Not for sending bomb threats but because the nature of surveillance, I am a target of the government so any outlier gets flagged pretty hard.
There was a university that received a bomb threat over Tor. They found one student who used Tor on the network at around the right time, and because he was the only Tor user, he’s in jail for a very, very long time. That kid was at Harvard, his persuer the FBI.
If you are going to use GrapheneOS, don’t be naive and think it will make you agency-proof. If anything it probably flags you to their attention.