But from a higher-level thinking point of view, neither of the requirements you mention mean a stub is necessary. I know this is a little nitpicky, but e need to step back from things like this to realize that the entire premise of a stub is only required because of previous decisions in the system.
The only things the user actually needs is (1) a way to find a seat, and (2) a way to verify their identity to agents. The stub happened to satisfy those requirements, but they could easily be solved in different ways (like Southwest has done).
That's the biggest problem with this entire article, it's only thinking about the last step of design decisions, so it's not going to come up with very innovative results.