The Big Names in treat training promote pulling food so that the animal (in this case a parrot) is fixated on the food. For them, its all about rapid training. This is understandable when you understand that they are getting paid by the hour or event to teach the process. The parrot trains-up rapidly, they get paid, and asked back. Harsh, but from their point of view it makes sense.
The other part of this process comes from large organizations, i.e. Zoos, etc... Here because of the volumes involved, feeding a specify volume at a specify time takes the Human out of the equations. Thus, the animals get feed, none of them starve and the system can buy, inventory, feed and most importantly, budget.
At the end of the day, it is important to understand the source of the information and why, for them, it is important in their specific World.
For us parrot owners, we can incorporated their systems into our homes. But why? After all, we are in it for the long term loving relationship! Right? I do not see a starving parrot being a happy, trusting parrot, but that's my belief.