“The general consensus has been that there is more Fifth Amendment protection for passwords than there is for biometrics,” Andrew Crocker, the Surveillance Litigation Director at the EFF, told Gizmodo in a phone interview. “The 5th Amendment is centered on whether you have to use the contents of your mind when you’re being asked to do something by the police and turning over your password telling them your password is pretty obviously revealing what’s in your mind.”
What’s that got to do with using a thumb to unlock the phone?
Sure, but what does your original comment have to do with the thumbprint?
The cops can coerce or force you to use biometrics to unlock your phone, but they can’t coerce you into giving up your passcode without a warrant.