Does it need to be exactly the same? I assume it's a perceptual hash with a liveness check.

This feels like a flippant response. The question you responded to was ‘would the hash of the iris would be the same?’ It isn’t as if you’ll get an identical image of the iris every time, and hashes tend to behave chaotically for even slightly different values. If we compare this to something like password salting and hashing, it isn’t clear how we can maintain the constant salted hash value if we swap the password for a digital representation of a person’s iris.