No, I bought 2 used cars in 2014, my '09 VE SS, and a Forester for the wife. both definitely show 10% GST. So the wifes '08 Forester reads $12,500 plus $1,250 GST - total $13,750 they did also add an "Admin fee" of $295 so just over $14,000 all up. Similar for the SS something like just under $18,200 plus $1820 GST - $20,000 total including GST. The dealer definitely is subject to pay 10% GST on a used car sale. Of course if the dealer incurred GST charges in the course running their business they can claim back GST that they have paid.
Edit - The GST on Used car has nothing to do with GST having been paid on the car as a new car. If a car is sold numerous times over its lifetime by licensed dealers, 10% GST is payable every time the car is sold by a licensed dealer. If the car changes hands many times (by dealers) the government reaps the GST every time.