Ultimately, when you choose to enter a duress PIN that will wipe your device, you have to recognize that choice may have legal consequences. I don't like the amount of power our government has at the national border when it comes to detaining and pressuring citizens, but our Constitution explicitly grants it at least some of the power it now exercises in that context. If your threat model includes US state actors at…
the funny part is he didn't enter the pin he gave it to them and they entered it..., not sure if it makes any difference but there is a certain irony to it that it was the non warrant based search actions (which might be legal at the border) which lead to the erasure of data
Lying to a federal officer is a crime, IIRC, and if the lie results in destruction of evidence, the person who told the lie is probably accountable for both crimes. This isn't a lie with plausible deniability: you have to set a duress PIN, understanding what it does, and then communicate that PIN instead of the unlock PIN.
A duress PIN to wipe the device don't exist to absolve the owner of liability... It exists for when compromising the device could get people the owner cares about killed or disappeared and the owner considers their own liability, disappearance, or death a preferable outcome.
It is an extreme solution for extreme scenarios. People need to be sober in weighing its use.