The magic number tire model from ACC also has a defect. 5 contact points are better than one as AC offered, but still not really up to date. Therefore the behaviour is more script based. You get the maximum grip at 28psi, which is unrealistic because the contact area gets smaller as the grip increases. Even 1 psi less will cause a noticeable drop in lap times, whereas in reality the racing teams try to set the pressure as low as possible, which is why minimum pressures were prescribed in racing series such as Formula 1 and DTM, and even then the teams tried to artificially increase the pressure for the tests using tricks like preheated air in the tyres. It may be that the behaviour in rFactor2 is exaggerated, but it is basically correct, unlike ACC. Of course it is also easier for a generally much simpler tire model to integrate features like air pressure loss and aquaplaning, which here are simple routines instead of simulating the tire in its realistic behavior. The question is what you prefer. I prefer the model of Rfactor2 because it feels much better for me.