I just wanted to offer a quick update on the battery drain issue I was experiencing.
After getting the car back from the dealership, my wife and I changed our driving routine to ensure that we never drove the car on those 5-minute, 2-3 mile trips more than six times in a row. Since making this change, we have not experienced a dead 12V battery once!
Based on this and the gradual voltage loss over time I observed with LeafSpy, I'm comfortable saying that the dealer's suspicion (and that of some here on the forum) that the car wasn't able to keep up with the accessory drain over those short trips was correct.
Hopefully this is helpful to someone down the line