Couldn’t GrapheneOS provide a special pin which boots into an “empty”session? Where the user can install some default stuff to not look suspicious?
They said they don't bother because it's non-trivial to implement convincingly, so they don't bother, lest it gives people a false sense of security. For instance, if you do this, and the adb logs aren't scrubbed, then that's massively suspicious and that'd still you in legal hot waters.
People are doing that in Belarus (since 2020 the repression still continue). You also need to create a convincing profile and story for all the usual apps. Alibi if you wish.
im not sure if grapheneos does or not, but it's not a novel idea, and often will only be a delay tactic.
forensics will reveal the other partition(s), and then you're in the exact same position having to answer "what's the other partition, provide the password"
Right, they should restore the phone to a user-picked previous state, as opposed to wiping it clean.