You would have a point if on the back of the game box it didn't say..
"Unauthorized copying, adaption, rental, lending, distribution, extraction, access or use of this product or any of it's trademarks or copyright work that forms any part of this product are prohibited"
You need to extract info using external tools from the game and then adapt it to mod create these cars. That's two strikes right there.
Potentially this whole affair could be damaging to PD also, if manufacturers get wind PD has done nothing to stop cross-manufacturer swaps, they may not wish to work with them in the future. To many of them gaming is a branding exercise, having your car improved with a rival brands crate-engine portrays a negative image for their own engines. They won't like it, and that's the reason why you rarely, if ever, will see such a thing licensed in a game (in it's original content/code). You may say this is minor but this game is a huge brand in itself and as such gets huge exposure not only throughout the gaming world but inside the motor industry itself.