But then the clock app is littered with old alarms, like it's just beyond them to create a one time alarm that's deleted after it's done.
Me: "Siri create a one time alarm for 30 minutes" Siri: "The alarm is set for 1:05 AM" ...
It was 12:11AM at the time, seems it misinterpreted asking for a one time alarm as 1 o'clock and added five minutes to it.