It does mean that. You can't be forced to divulge information in your head, as that would be testimonial. But if there are papers, records, or other evidentiary materials that are e.g. locked in a safe you can be compelled to open it with a warrant, and refusal would be contempt.

They need to prove that those materials exist on the device first. You can't be held in contempt for a fishing expedition.

You need "probable cause to believe" which is not as strong as "prove" but yes, it can't be a pure fishing expedition.

I know it seems like an incredibly dubious claim but the "I forgot" defense actually works here.

It's not really that useful for a safe since they aren't _that_ difficult to open and, if you haven't committed a crime, it's probably better to open your safe for them than have them destroy it so you need a new one. For a mathematically impossible to break cipher though, very useful.

FaceID and TouchID aren’t protected by that as I understand it.

That's correct, they are not. A complete failing of legislation and blatant disregard of the spirit of the 5th Amendment.

So do not have biometrics as device unlock if you are a journalist protecting sources.

They are considered to be more like keys to a safe than private knowledge. They also can't be changed if compromised. A sufficiently unguessable PIN or passphrase is better than biometrics.