Do these cars deserve to be in GTS?

[iName]

Can't say the 599 GTB looks bad. The reflections may be too "plastic".
The Elise 111R needs some work, though. And some parts of the Integra do.
And the R32 GT-R is modelled all wrong. The face, particularly. The standard version has better proportions.

All cars in triple-A racing games nowadays (yes including GT) are laser scanned, so unless the scanner was faulty, there will be virtually no flaws in the shape of the cars whatsoever.

And if you want to know what a plastic-looking car texture looks like, take a look at FM4's cars. That's what a plastic car looks like.