I must admit I have a hard time understanding how the system works in the UK.
Over here you order the car, wait a couple of days to get an estimated delivery-time, wait about 3 weeks and then get the confirmed build-week and delivery-time.
We don't even have a order tracker over here.
To be honest, I think much of the problem here is Volkswagen's UK company - they seem to make up the rules as they go along, and to change them whenever it suits.
Perhaps it's the logistics of the production lines, UK cars are right hand drive where as most other countries are left hand drive vehicles, as the factory is producing for many countries, perhaps the majority of production is for other countries with the 'odd' slot for the rhd countries. So depending on when the order goes in, it may have to sit and wait until the batch for a particular zone is going to be run.