I saw that too but didn't feel like expounding the effort of rebuttal at the time. I read it as the author thinks the stock (non-BTTF) car weighs 3200 pounds.
The facts as I understand is the car's curb weight is 2712 lbs while the gross weight is 3180, where the gross is the max weight the car was rated for when it left the factory (passengers, cargo, etc.). So saying the car weighs 3200 pounds in stock form is almost always going to be erroneous unless you're carrying ~500 pounds of shat... or 300 pounds of shat + one 200 pound human... or whatever other combination.