[bodz]

Not false. Police can ask for your password, and if you do not give it to them, you can be arrested pending a hearing with a judge. The judge can then compel you to give up the passcode (though they probably won't unless there's reasonable suspicion that you're hiding something - but again you're just banking on the judge's mood/feeling at that point), and if you don't, you can be held in prison until you do give it up.

The "questionable constitutionality" of it is irrelevant since in practice until there is a higher ruling on this, if you don't want to go to jail, you must give up your passcode.