Do you mean when the alarms arms itself after engine shutdown? Cause that last paragraph don't make sense.
It's true you can set it too arm automatically 30 seconds after you turn off engine and close doors. But won't lock doors.
Then you would have to disarm alarm the arm alarm the doors to lock.
If you get central locking hooked up to your alarm with it.
Also with the alarm you should be able to tell it automatically re-arm and lock doors if you disarm alarm then wait 60 seconds without opening any doors.
This is just in case you unlock your car then forget something from the shops then in excitement you run back to the shops forgetting to lock your doors.
So on and so on.
Cheers,
Jim