There are 10 cars in game, 1 car on the road and you are correct, 1 environment. This does free more space.
It also doesn't have car decals, it's 1 colour, there are no particle effects, no dynamic lighting and the surrounding objects around the road are low resolution and dull. For every one thing that looks good in GT:HD there are about 3 things that don't.
Personally I don't think GT:HD looks that good when moving and believe me, when you are playing, it's that slow you might have to double take to make sure those frames are ticking by. It's one of, if not the slowest racing game I have ever played.