A kid who doesn't get full of food at dinner time is more likely to enjoy icecream than a child who gorges himself on dinner, then has no room for dessert. It's not starvation, it's motivation.
That said, you don't *have* to use foods as a reward, they are generally just the easiest reward to use when training.
Technically, you could say that the Womach brothers are not professional trainers.
Let people watch us try multiple parrot taming techniques on untrained parrots. Let them see what works and what doesn’t, and let them watch as we overcome every challenge a bird throws at us!
They started out training using flooding techniques. They took a technique commonly used by millions of breeders and people, perpetuated it and sold it. They also had ridiculous marketing techniques. The one I hated the most was when they were "barreling over cliffs and swimming with sharks", making it sound extremely dangerous. The reality? They were in a helicopter, flying over cliffs, and swimming with black tipped reef sharks, a species not known to be very dangerous to humans. Much like the nurse shark.
They love birds, and they mean well, but as far as I can tell, they are not certified trainers. You can get the same information, if not better, from well respected trainers for less.