Disturbing to hear that even as an American citizen I only have rights when I'm on the ground in specific sovereign territory, of which the border (which is obviously American soil) is exempted.

With respect to the phone, I'd say one has the right to delete everything on one's phone at any time. There is no evidence that the person in question was "destroying evidence" because there was no evidence - or suspicion, or charges, or anything substantive.

I think the authorities just got ticked off by the duress password, and they're flinging mud.