Yup its true - with my old car it was click once to lock, click twice to deadlock.
But with the GTi you click once to lock and alarm, click twice to make it less secure!!!
The 2 clicks is supposed to be used when you want to lock the car from outside, but there are still people inside. For example, when I have my family in the car and I fill up with petrol, I tend to lock the car when I go to pay. With the 2 clicks, I can lock the car, but if anyone needs to get out of the car, they still can without setting off any alarms etc.