This trial made no sense. Try stepping on your accelerator and brake at the same time and see what happens: https://podcasts.apple.com/us/podcast/blame-game/id111938996....
2. In my car, if I step gently on both pedals, they both take effect. (Which is reasonable: starting uphill is a thing.). If I step harder on both pedals, the car chimes at me and the motor output is reduced automatically.