According to https://security.apple.com/blog/imessage-contact-key-verific..., the actual verified hash of the account key is stored in an end-to-end encrypted CloudKit container and merely linked to from the contact card.
You can also try exporting the contact to a vCard .vcf file using the Share Contact button. I believe the iMessage key verification info won't be included. (But as you noted the most important thing is that it can't be modified)