Sunroof Alarm is a single beep only?

It was such a nice day today that I popped the Sunroof open on my shinny new 2013 Prius which I haven't had a chance to do until today. When I parked the Prius and opened the door to get out, I heard a 'single beep' sound. Confused and not knowing exactly what that 'single beep' was intended for, I proceeded out of the Prius and touched the button to lock the doors. But due to my absentmindedness, I then noticed that I had left the Sunroof 'OPEN'. However, I couldn't believe that the doors actually locked and the Prius didn't do any other kind of additional alarming with the Sunroof left open. So, I presume that this 'one single beep' I heard when I opened the door was intended to inform me that the Sunroof was left open. It's a good thing that I wasn't in a hurry today and noticed it because I didn't know what that single beep was meant for.

I checked the Torque app and custom CSV file, but I didn't notice anything that would change this single beep for the Sunroof, is there one?

It is just so funny to me that by default Toyota has a continuous beeping when the Prius is in reverse, but only a single beep for the Sunroof left open. I have to say Toyota really should swap these two default alarms sounds around since no one cares for the continuous reverse beep anyway.