That's a reasonable explanation, but not what happened.
On the first occasion, I was listening to podcasts. When I started listening, there were many in the queue. After listening for about 45 minutes, Listen Up stopped because there was nothing in the queue.
On the second occasion, I don't know when it happened, but I definitely didn't leave it playing overnight, because it would have kept me awake.
Anyway, if I had left Listen Up playing overnight, I don't think it would have downloaded the podcasts again.