Presumably the orbs produce a verifiable type of hash. E.g. whatever output it has is also encrypted with their private key + some salt and you can always check if what a user provides has that.
1. User has a "fake" biometric A, generated via GAN or [1], that's cheap and easy to produce.
2. Suppose they can present A to any orb device, generating hash(A), which signs hash(A) using its built-in private key as usual.
As long as the user can generate a fake iris biometric scan accepted by an orb, no other part of the system needs to be compromised for this attack to work.
1: http://iab-rubric.org/papers/ICPR14_1649_FI.pdf , note that liveness detection is a cat-and-mouse game