All cars and upgrades have a finite number in terms of possible specs. Finite value of grip, acceleration, speed, etc. Yes, there are millions of possible configurations, but AI tools can analyse all that data and propose sensible race restrictions to minimize (or eliminate) the possibility of players' cars being OP.
In early GT games we had a considerable freedom to choose many cars for a specific event and this "freedom" approach would break some events for sure, but now we actually have very good tools to get the best of both worlds.