if you get searched by a law enforcement officer and then proceed to quicky destroy the pocket contents you can be assured to raise suspicion. this was a stupid thing to do by the person in question regardless of laws or device properties or privacy stuff.

if you move the example from a phone and encryption to something more mundane you can see that this is not a smart move and you will most likely face penalties or atleast a bad time with enormous amount of questions and further poking at you.

it was already pretty much impossible to get an encrypted device past US Customs more than 15 years ago.

even though that is not a good thing, people should know this by now. just use a less suspicious device or OS and likely they wont even bother to search it... Better to avoid than to try and cure.