Hey sek.

It sounds as though you have fallen victim to a dealer who is either ignorant of the supply issues, or lied to you about the delivery date to secure a sale. There is no way you were going to recieve a factory order in February when ordering in October - not unless the car was already in the system (which is a situation VGA are stopping to help relieve the pressure on legitimate orders).

Beyond that, ETA means Estimated Time of Arrival. So by definition, yes, an estimate is a guess (hopefully based on recent experience). NO ONE can tell you for certain when your car will arrive, because once it's been built and delivered to the dock in Germany, the rest is really not up to Volkswagen - the dealer can influence the result by a few days by pushing the car through dealer delivery quicker, but that's nothing compared to the rest of the delays which can occur from that time.

There are multiple ETA's which people quote around here. The ETA that is in their NADCON system is when the car will dock in Australia. Note that I don't believe that ETA actually matches up with the actual shipping companies (as there are multiple routes), but I could be wrong.

If the car has an arrival in Australia ETA of May 4, it probably hasn't been built yet, so they won't have a VIN. They might have a build week though. If they don't, maybe they've only got an ETA for production...

The system VW use is called NADCON.
This system has multiple screens. But the "Production ID" information (including build week, day, number, factory, VIN, engine number etc) is on the "Extended Information" table of the "Order / Order Details / Car Configurator" screen.
There is also a "Order / ETA Data" screen which has a whole heap of checkpoints with estimates. The dates are added in automatically by "the system" as the car progresses through the process. Even on that, the "Arrival at final destination" and "Arrival at dealer" rows are not populated initially.
You could ask for a screen capture of the "ETA Data" from NADCON.

Hope that helps (sorry if any of it is "short", I need to get home!)