Earlier quoted context omitted.
Knowingly providing a PIN that would erase evidence is going to get tough in court. But the man was also hated by the cops because of his activism. They were going to catch him for something, some day. This incident just provided the necessary excuse to lock him up.
How can they prove that? What if it was a glitch?
That shouldn't be too hard. Get someone from Google or someone with any tech knowledge to explain to the judge how phones normally work, what encryption keys are, the implications of wiping an encryption key, and then get someone to show the difference between entering a normal PIN wrong several times and entering the duress PIN. You just need to convince the jury (or judge, if there is no jury for whatever reason).
People have gone to jail or have been executed for less than a glitch. Theoretically a highly charged particle from space could've messed with exactly the right transistors exactly when entering the correct PIN and trigger the wipe process. There is no way to prove that didn't happen. But you don't need that kind of proof.