duplex insurance

Just got a quote from NRMA insurance. For a duplex i have to buy 2x policy's and 2x Landlords insurance. Is this normal? I thought it would be 1 building policy and 2 landlords? Anyone?
FWIW, when I had my block of 4 units, they were all on one title. Hence, I ended up with 1 building insurance policy, but 4 LL insurance policies.

Do you have separate titles which causes the insurance co. to push you to 2 building policies?

But is there much difference between, say 1 x $500,000 policy vs. 2 x $250,000?