Fallacy? Rubbish!!!!!!This is a fallacy. Natural does not always make something better, and unnatural things are not always worse than their natural counterparts.
What we want for our birds is often vastly different from what Nature wants from our birds. Birds in the wild eat diets higher in calories and fat because they are far, far more active than their captive cousins. Not only this, but wild birds are nesting, breeding, and foraging for food - all of which put a strain on their bodies that are not always conducive to a long lifespan.
So if you want your bird to live a fraction of its potential captive lifespan in the name of feeding it what you think is "natural", then a seed and fresh food-only diet will probably work for you. However, be prepared for ridiculous vet bills and a lot of misery down the line when your bird is suffering from liver failure and other diseases associated with long-term nutritional deficiencies.
Just my two cents.
Where you get your facts from?
Actually if you want to shorten your birds life Feed them pellets.
This is far more truthful than your false claim, and scare mongering.