Technology

Because the reboot is not cosmetic. The duress PIN destroys the key derivation material, and a device with no keys has nothing left to boot into, so you get the restart and the blank slate. There is no version of that which looks quiet.

The thing worth adding to your instinct: quietly unlocking to an empty phone has the same problem as the flashy version. An empty phone is itself a statement. Nobody carries a device with four apps and a two week message history, so a careful look at an empty phone raises the same question the reboot does, just more slowly.

What answers your instinct properly is quietly unlocking to a phone that is full. A complete ordinary device, real apps, real photos, real message history, while the sensitive environment sits behind a separate credential and is stored so that it reads as encrypted random noise, which is what unused encrypted space looks like anyway. Nothing is destroyed, so the phone just unlocks and keeps working, and there is nothing afterwards for anyone to describe as destruction.

The honest catch is that the decoy has to be genuinely convincing, and keeping one that looks like a real life is ongoing work that most people quietly stop doing after a month. A thin decoy is worse than no decoy.

Disclosure: I work with DeniableOS, which is built around that approach, so weigh that accordingly. GrapheneOS is excellent, and their own statement this week says the same thing you are circling, that people should think hard about a wipe because it can carry physical or legal consequences.