Having the ESC and Receiver separated is a key feature. People can choose to use whatever Receiver and TX they like. Having them integrated defeats the whole purpose. Integrated ESC and Receiver is exactly what Mini-Z is. And IDT is not meant to compete with Mini-Z as it's a totally different class. But I understand many people will still try to compare it with Mini-Z...
BTW, I happen to have tested the car and discussed with the designer before. I have ordered one immediately after testing it.