I am certainly puzzled as to what benefits iris recognition security brings to the evolving story of the phone..
Fingerprint recognition has been a terrific development - secure but very fast, and naturally fits how you hold a phone and start using it; and for payments, password apps, banks apps, etc.
Any kind of face-located recognition will require a deliberate move to angle the phone correctly, and possibly bring it closer to the face. Surely that's a less-natural gesture as you pick up/retrieve/start to use your phone.
Iris-recognition technology is certainly very clever, and has come on leaps and bounds even in the last few years. Using 'IRIS' for speeding through immigration at Heathrow after a long-haul flight always worked terrifically, with or without contact lenses. Had to remove glasses though. Shame it had to go really.
And yes, there are assorted eye conditions that affect iris imaging, and iris permanency, from dry eye keratitis, dystrophies, glaucoma, and specific iris conditions such as uveitis, pigment dispersion, psuedoexfoliation, naevi.. the list goes on. But if a changed iris means you get into your phone by typing in your passcode again, much like if the TouchID fingerprint can't read your fingers, then I start to ask what is the point anyway?
Yes, I'm sceptical that this is a beneficial and non-troublesome feature. Happy to be proved wrong of course.. I do love new technology!