The final interview was set — or rather, it was announced. The founder messaged at 1:30pm to ask whether the candidate could join at 2pm, which gives the arrangement the shape of an invitation and the timetable of a summons.
The candidate was not available at thirty minutes' notice. They asked, politely, whether the conversation could be moved. The company's answer was to end the process: asking to reschedule the final round was, on this reading, the disqualifying answer.
Thirty minutes is not a scheduling proposal. It is a test, and the only passing response is yes. The candidate failed it by having something else on at 1:30 in the afternoon — and a loop that had already reached its last stage closed on the spot.