Finding
Technical availability asks whether the system can perform. Functional Availability asks whether the intended person can reliably complete the real pathway under ordinary conditions of use.
How the mechanism works
A technically valid pathway can accumulate friction through sign-in, prompts, navigation, recognition, physical reach or support dependencies until the intended outcome is no longer reliably achievable.
Evidence boundary
Functional availability is specific to an intended outcome, operator and environment; it is not a permanent property of a product.