Partially this makes sense to clear a relatively low risk person into the program before they enter the country but a few things seems off to me. IAH & SFO make sense because of the multitude of international flights that connect to participating countries (where foreign residents qualify to GE) but AUS is a relatively low foreign travel volume airport. YVR somewhat makes more sense to me because of preclearance and the number of international connections but to less qualified residents. Canadians will do Nexus anyways.
It also means that there will have to be an office at each airport to do such interviews before entering the country which means more space in the airports immigration area & more staff.
One additional question, what happens if someone is turned down while in that interview? It's less common as people are conditionally approved but it does happen. If a major disqualifying issue comes up during the interview it seems highly possible that the foreign traveler would also be denied entry due to such information.