Yes, but an arrest requires evidence that you actually committed a crime, whereas border searches require no particular standard and are conducted relatively in

Yes, but an arrest requires evidence that you actually committed a crime, whereas border searches require no particular standard and are conducted relatively indiscriminately. Refusing to unlock your device is not a crime in itself. (However, lying to a federal agent is a crime, so it's important for anyone attempting this strategy to be forthright about their refusal, rather than trying to trick the border agent with fake data or whatnot.)