That matches my understanding too. Unfortunately it sounds like the poster was suggesting to wipe the device after the government requests access, and was probably not planning on telling the officers about the trigger.
The theoretical scenario was the government seized your device, they don't give it back to you. You decline to give them they password. You don't say anything else, you have the right to remain silent. You aren't not telling the government to do anything. You don't suggest they scan your fingerprint. They are in charge, you are cooperating with lawful orders ("provide your fingerprint").
There are videos on youtube where the lawyers tell you what your rights are at traffic stops, also there are ones that talk about the different rules when coming through immigration. These can be painful to see when they show the ones where cops ignore limits.
So at the border, they tell you that you are legally required to provide your finger print, you do that, and don't say a word. I'm sure it will be a bad day for you, regardless of how it works out after years of litigation on whether it is your duty to tell them how NOT to unlock your device.
With fingerprint unlock it's not your choice. That's what makes it clever. The cop can grab your finger and hold it to the scanner while you tell him not to do that.
Presumably you must disclose that "doing that" would wipe the device... and you better hope this is caught on some neutral party's camera so there is a record of you saying that.
I am not a lawyer, I am just "making up" what exculpatory evidence I would prefer to have on my side when potentially confronted with a charge of destruction of evidence after pulling a stunt like this.
