Yep, the story is totally different for non-citizens.

My plan, if this ever comes up, is to refuse to unlock the device, ask for a lawyer if they hold me, and wait it out. I already make sure to power down my device before I hit customs just to be sure they can't compel my fingerprint.

I couldn't advise my wife to do this, though. It's likely that they'd revoke her green card, deport her, and basically wreck our lives. At least she (probably) has nothing to hide....