It’s unbelievable that you’re not supposed to use cruise control when passing? It sounds like common sense to me: you’re supposed to be accelerating to get past the other car.
It's unbelievable that something so unreliable is allowed to be built into cars, and then people are learning work-arounds in driving school for it, instead of just getting rid of it entirely.
Cruise control has been around for decades, and is a tool for maintaining a constant speed. When you're passing someone, you should not be maintaining a constant speed. Cruise control is therefore the wrong tool for that situation. Driving school teaches you to use the right tool for that situation, which is the accelerator.