The Mk4 shuts down power after 60s of databus inactivity.
Databus inactivity occurs when the ign is off, all doors and windows and sunroof are closed, and the car is left alone.

You can observe this by leaving the boot open, and shutting elverthing else and locking the car. Use a stopwatch. Around 60s to 70s after the car is locked the Mk4 will shut down.

If it doesn't it indicates you have ongoing databus activity, you would need to monitor the databus to see what device is not shutting down (it may well be another device which is the issue)