It's more a policy problem than a phone problem. Apple could add as many pins as they want but until there are proper legal based privacy protections, law enforcement will still just be like "well how do we know you don't have a secret pin that unlocks 40TB of illegal content? Better disappear you just to be sure"

For as long as law enforcement treats protection of privacy as implicit guilt, the best a phone can really do is lock down and hope for the best.

Even if there was a phone that existed that perfectly protected your privacy and was impossible to crack or was easy to spoof content on, law enforcement would just move the goal post of guilt so that owning the phone itself is incriminating.

Edit: I wanna be clear that I'm not saying any phone based privacy protections are a waste of time. They're important. I'm saying that there is no perfect solution with the existing policy being enforced, which is "guilty until proven dead"