Yes the difference come from a close parsing of the 5th amendment, telling cops the password or code for a device or safe is pretty clearly compelling speech and adverse testimony while allowing cops to gather fingerprints and DNA has long been held as allowed so biometrics were analogized to that. It's also similar to the rule that cops can't force you to tell them the code to a safe but they're allowed with a warrant to destructively open the safe (if it falls under the terms of the warrant). Combine those too legal threads and it's at least reasonable to see how that line gets drawn from previous rulings.