The user claimed to offer a password to access the contents of the device, and instead offered a password that deleted the device. That is false testimony / lying to an investigation, and is almost certainly punishable in itself.
The fact that the feds are using an obscure law to argue that he destroyed property to prevent it from being seized shows that they're reaching here.
This doesn't pass the sniff test. Consider the following:
Cops: "where were you on the night of the murder?"
Suspect: "at work"
Cops: "You're lying, we found surveillance footage of you near your girlfriend's apartment"
Suspect: "ah-ha, what I actually meant by 'at work', was that I was mentally at work!"
Of course, there's some grey area where the suspect gives cagey or vague answers, but in this case by giving a duress pin, it's pretty obvious the intention was to deceive the CBP officer.