You are mostly true. RWD has the drag racing advantage and on most tracks the RWD cars can do just as good as the AWD ones. The difference only becomes apparent when you have two expert drivers racing a RWD and AWD car against each other. The only place in Pro Street where this actually becomes apparent is in speed races. At speeds as high as 250MPH you can feel the rear end of a RWD car losing grip. I've tried the Zonda and it was the scariest thing I've ever done in that game. The AWD on the Lamborghini Murcielago LP640 is the thing that makes it so stable which is why so many people like it.
I agree completely and had the same terrifying issue with a few rear wheel drive cars in the game.