Check your strata plan management statement – it should be somewhere in your purchase documents. It may be your neighbour has declared this to be a dual occupancy for their own convenience when it is, in fact, strata.
NSW strata law specifically allows two-lot strata schemes to have separate insurances for the individual lots. Just make sure you have at least one minuted meeting with your neighbours a year to make sure you are on the same page and fulfil your legal obligations.