This is false. If you can image and wipe your phone on the plane before landing, and write those random bytes to a usb stick, the usb stick will appear blank, because encrypted data is noise. You land with a factory blank phone. You clear customs and get where you are going and restore your phone.

Substitute cloud storage for a USB stick if you do it at your departure hotel.

There are absolutely technical solutions to the implementations of tyranny. Otherwise we wouldn’t bother with encryption. Violence can’t solve math problems.