This is a different objection than the original objection. (effective accuracy vs specific bias).

With a pervasive system, unless people are hermits, they’ll get scanned periodically, and with other bits of information the changed face can be correlated with the same person (I go into a salon looking one way, come out different, go into a boxing match, come out different, but I’m following my routine and go to the same subway stop and convenience store and use the same payment method, etc.)