Apple Document Writers - We're only at macOS 14.2 & watchOS 10.2 beta and not 17.2 yet :)

iMessage Contact Key Verification
New Features
With iMessage Contact Key Verification, users can choose to further verify that they are messaging only with the people they intend. iMessage Contact Key Verification uses Key Transparency to enable automatic verification that the iMessage key distribution service returns device keys that have been logged to a verifiable and auditable map. When a user enables the feature, they will be notified about any validation errors directly in the Messages conversation transcript and Apple ID Settings.
For even higher security, iMessage Contact Key Verification users can compare a contact verification code in person, on FaceTime, or through another secure call. They can also choose to create or edit a contact and save a public key to turn on iMessage Contact Key Verification with that person.
All devices signed into your iCloud account must be on the minimum supported version of iOS 17.2 Beta, macOS 17.2 Beta, or watchOS 17.2 Beta. If you wish to keep using other devices on older versions of the OS, you will need to sign out of iMessage on these devices in order to enable contact key verification. (111356044)