Did we ever decide if the language can be interpreted to include biometric safes?
Yes. You can be legally compelled to provide any biometric, even blood sample, by warrant. That's why few folks recommend biometric security, along with its fairly dismal performance unless you go with high end systems.
Compelling to provide passwords and encryption keys are... more mirky. There is no law on the matter. Some courts do not see it as a violation of the Fifth Amendment, some courts do. Worst case, if the evidence could give you a longer sentence than contempt of court, you shut up and take the contempt of court.
Though in some states with a broken or corrupt judicial branch, like Pennsylvania, we put a guy in prison for 14 years for not paying up in a divorce case, when it wasn't known or proven that he actually had access to the funds in order to actually do so. Fed max is 18 months. Mind you, he did nearly a decade and a half without trial or being found guilty of a crime.