Trezor devices also have the passphrase functionality. Using a passphrase is akin to the scenario I described above with using a hidden encrypted volume; you can give away the PIN or encryption key to the "dummy" wallet, while keeping you real wallet hidden. This all relies on the hidden wallet not being known about by the attacker, which in addition to keeping it a secret, also means not having it obviously linked to your "dummy" wallet via the blockchain.

Using a passphrase is a good additional security measure, and everyone with a hardware wallet should be using a passphrase. In addition to the plausible deniability as described above, it also helps to mitigate against physical attacks on the device itself.