So, there's a bunch of factors going on regarding crap like this. The general argument is that the passwords are protected by the Fifth Amendment to the Constitution of the United States, the protection against testifying against yourself. While biometrics are not.
Then there's the Constitution Free Zone established by the DHS and ICE and upheld by some judges depending on how related to immigrant control your detention by law enforcement is. The Federalist Society doesn't like non-nationals, and if you can't prove you're an American in the zone (100 inland from any US border) then you get zero Constitutional protections.
Then there's the matter that law enforcement can lie to you to convince you to authorize searches. So they may insist you are required by law to open your device for them when you are not. This is why you don't cooperate without a lawyer. For now police are not allowed to give you a fake lawyer and lawyers, even public defenders, are required to adhere to a code of ethics to serve in the client's interests. But this may change in the next few years as rights in the US deteriorate.
Then police departments in Cook County (Chicago), New York City and Los Angeles have all used the $5 wrench method to force detainees to open their devices. While there are allegedly laws against this sort of thing, it doesn't slow down the precincts, and judges sometimes uphold found evidence in court the way they'll uphold coerced confessions.
So it's really better not to interact with law enforcement ever if you can avoid it, and to have a high powered defense lawyer if you can afford to establish a legal relationship with one. If you're doing something the state wouldn't like (say, operating a mutual aid program) then look into having multiple accounts on your phone, one of which is pristine and can call your grandma. Then you have the option to unlock to that account rather than the one that has your life's history (and all your CFAA violations).
