Originally Posted by Droid13

My mistake. I was thinking about the "passive arming" feature of the alarm system (which is normally off). While the system can be programmed to arm automatically, it does not lock the doors. In fact, the passive arming is primarily useful when you don't want to lock the doors, as locking the doors causes the system to arm anyway.

This automatic exit locking (as opposed to the automatic relock function) seems to be something different, perhaps a later revision to the firmware. Mine being an early 2007 has no such feature, just the normal auto relock.