I may be wrong, but when you “buy” off the plan, what you have done is enter into a contract to purchase a particular lot in the future. In real estate a purchase can only occur when their (sic) is a titled property. So your purchase does not take place until the strata subdivision is registered, and their are title documents for each lot.
I’m more interested in what impact (if any) the delay in registration has had on the OP. We are getting many stories about how the new systems in place in NSW Services, Planning and related departments are causing delays and additional expense. I suspect, as you say, that’s all that’s happening here.