I'm not only against this due to it being trivial for someone to see you're using GrapheneOS (e.g. via the boot hash while booting), but I also think it's extremely important to ensure GrapheneOS is not stigmatized, and not being something people have to hide using. It's an open source privacy and security project. Because it works, people in all walks of life are going to be using it, same as something like the Tor Browser.
I mention Tor, because it has, and still has a bunch of stigma associated with its use, exactly because people assume that if you're using it, you must be doing so for nefarious purposes. The "if you have nothing to hide, you have nothing to fear" crowd would love for projects like Tor and GrapheneOS to start trying to mask themselves, as it furthers the narrative that only sketchy people would want to use them.
I understand you might not like this response, or your unique situation might not permit this, but I encourage everyone to be loud and proud about using things like GrapheneOS and Tor. Privacy and security for everyone should be normalized, not something people hide.