In a strange twist, I called Vic Roads and asked them about my car.
They said that the officer who issued the defect to me, has not contacted Vic Roads to list the car as defected. As far as they were concerned they have nothing at all on file to say my car is currently defective, and as such they have no plans to cancel my registration at the end of the 28 day notice period.
So, if I were to turn up at Vic Roads tomorrow with a RWC, their response would be 'huh, what's this for?'
The guy at Vic Roads recommended to obey the conditions of the defect notice and turn up with the defect notice, RWC and car, so they can check that all the work required on the notice as been completed. I argued that according to the Vic Roads website I only need to bring the car in if there is a defect notice on the windscreen, (there is a odd loophole that if you replace the windscreen for RWC they don't need to see the car.) However the Vic Roads guy was not convinced.
I'd be interested to see what would happen if neither the officer or I ever supply details of the defect to Vic Roads. I have a strong suspicion that the car would simply remain registered.