WRONG! I have brewed beer off and on for almost four decades. There is NO discarded barley or yeast. This should be the end.
All-grain home-brewer here - there's all sorts of waste in the beer making process. A common metric for all-grain brewers is mash efficiency, and most recipes assume 75% - meaning that the average home brewer is throwing out 25% of the sugars that are left in the mash. Pro's chase mash efficiency for costs, and even some homebrewers can get a little obsessed with it. Actual efficiencies can be 10's of percentage points higher or lower.
As the article states, there's protein losses too, as wells kettle and fermenter waste commonly called trub. Any way one can reuse this waste is a good thing. Although as other's have noted major breweries, and even most craft breweries likely already have a customer for the spent grain. It's likely not wasted very much even today. But more potential uses for them can't hurt.