These arguments almost always seem like encryption is about access to information but isn't encryption about understanding information? If they are asking for a key to decrypt then they already have access to the data. If you write a note nobody will ever have access to- say you slipped it onto Voyager 1, there would be no point in encrypting it. Encryption is to protect against (possibly) accessible data.

Old-school though experiment- I encrypt all my paper notes using a simple substitution cipher. They seize my notes and have full physical access to them. If they don't understand my notes can I be forced to explain my cipher?

If I comply and the unscrambled contents are "RedFalcon has delivered the ApplePie to the EndOfTheRainbow". This is basically another substitution cipher. Can I be forced to explain this under threat of jail if I don't explain it in a way they accept?

I realize modern encryption is way beyond this, and way beyond my understanding. Has the basic principle of access vs understanding changed?