A signing key you can rotate.

On most blockchains, the key that signs is the account. The address comes from that one key, so losing it loses the account, with nothing to swap in.

The XRP Ledger keeps them apart. An account has a master key tied to its address, and a separate regular key, assigned with a SetRegularKey transaction, that signs day to day. The regular key can be changed or removed, while the account and its history stay put.

SciPHR signs with the regular key on the device, released only by Face ID, and keeps the master key sealed in an encrypted backup it cannot open. Picture rekeying your front door after a copy gets out, without moving house. Expose that key and you replace it, keeping the account.

A key you can rotate makes a compromise a rotation, not a dead account.