It’s possible to lose one’s irises. Most identical twins have almost identical DNA. Then there’s the “right to be forgotten”, people on witness protection, refugees and immigrants who enter the system as adults, etc. I don’t think there’s an easy technical solution.

Blind twins* will need to carry an alternative. /s

Of course the technical solution isn’t easy, (or necessarily all good),

but that doesn’t make it any less likely, or intriguing to discuss the roadmap.

(You combine the scanned data together from both of those scans, regardless of value, as your recovery mechanism, by the way - accounting for abnormal anatomy in a defined, reproducible way is a challenge, not a barrier)