Two PINs, two sets of contents. If a laptop or phone is stolen, lost, or handed to somebody with no right to what is on it, the second PIN opens an ordinary-looking workspace instead of the real one. Built for equipment that leaves the office, and for the client material on it that you are obliged to protect.
MIRAGE exists for coercion by people with no legal right to your data: a thief, a scammer on a support call, someone who has taken a device off you. It must not be used to mislead a court, a regulator, an auditor, a customs or immigration officer, an employer conducting a lawful investigation, or anyone else you owe a duty of disclosure to. Presenting false contents to any of those is obstruction, it is a criminal offence in most places, and it breaches the Acceptable Use Policy, which ends your access without a refund.
If you are under a preservation notice, a production order or a litigation hold, that duty overrides any use of this tool. If you are not sure whether one applies to you, ask a lawyer before you use it, not after.