The constitution has been interpreted to allow the police to force your finger onto an inkpad for fingerprints. That decision was extended to allow the police to force your finger onto a biometric reader.

The 5th Amendment has been (so far) interpreted to only limit things that require conscious thought, such as remembering a password and speaking it or typing it.

I don't know about that exactly, but my understanding was that this is similar in justification to compelling a person to be fingerprinted or give a DNA sample. To me there does seem to be a fairly major difference between forcing someone to disclose information held in their mind and forcing them to provide a biometric. The former seems equivalent to compelling testimony against oneself. I have a hard time seeing the latter as compelling testimony against oneself, especially if giving fingerprints or DNA isn't.

IANAL but I think legally speaking that would be forcing speech. Biometrics are not speech.

It shouldn't be different. But law enforcement wants access and everyone who could reign them in seems to also want them to have access. Honestly it's surprising at this point they haven't argued that people can be compelled to give up their password using whatever means necessary.