Yes we are talking about GT3 and other cars like them. Obviously they are stiffer than road cars. You could buy any off the shelf aftermarket spring you want for a road car and it still wouldn't be anywhere stiff enough for a race car of the same model. We are talking about race cars not road cars. GT3 cars have spring frequencies of 4Hz at the highest and usually lower than that. That is a much lower figure than you would see on a aero dependant race car, which also use most curbs. They also have fairly high ride heights, as far as race cars go, compared to higher tier open wheel and prototype cars. If you want to take the GT class to the extreme you can look at DTM and Super GT where they have lower ride heights and stiffer suspension, almost getting into the prototype realm. They too ride curbs a lot. How stiff your springs are is also not as important as you might think when it comes to curbs. Ride height and bump rubber, to a lesser extent, is much more of a factor. When you run out of suspension travel and bottom out, you have big problems. In your video the Ferrari clearly bottoms out in the rear as it straddles the hump in the curbing. That curb is also MASSIVE compared to every other curb in existence. So big that the front splitters are hitting it, as you can see with the P1 Audi. The whole bumper and fender deform as the shock travels through them from the splitter hitting the curb. My knowledge of V8 Supercars is a little limited but I have seen them on that track on TV once and they bicycle their way over that curb. This is only possible through higher ride heights and softer suspension so that the car can roll that much without losing contact with the road immediately. The insane amount of camber they run is also a result of the roll angles they produce. I'm not trying to prove you wrong just explaining my point about racecars using curbs. Which is why I asked how it is in pCars 2 since in pCars 1 some cars react very violently to using curbs where as other cars in the same class can soak up everything.
Edit:
The curbs your showing should obviously be avoided by anything. There was enough space under the front of that Audi when it was on the curb facing sideways that you could crawl under the car. It didn't bounce off the curb it bottomed out and turned into a skateboard.
View attachment 648150