They said that they had enough data to make auto models for PS5, not that they will use these same models. So probably they scaled back to bring these models to run on PS4. The fully featured model will come to PS5. Clickbait title.
The game looks amazing and people comparing it to Project Cars 2 forget that this is a PS4 game and that game is coming to PC and at its highest you'll obviously get more detailed models.
But GT Sport makes better use of HDR and wide colour and those are more noticeable when running on an HDR TV. The models are close enough to the naked eye, especially during gameplay where you wouldn't notice fine details.







