I don't agree with that interpretation. It's literally "people should be eating more fiber at the same time they're throwing away a lot of fiber".
Poor people aren't scraping the food stores for dietary fiber or fretting about how they'll afford a modest reduction in the long term risks of certain forms of colon disease.
For goodness sake, one of the tips is to make roast squash seeds. That's not eating the unpalatable part, people buy those.

It's not "eat like the poor" it's "cook like a restaurant". That thing you don't need for this recipie is great for this other one.

I think you are both under and overestimating how much people know about cooking. People will trim off the better tasting parts of food and throw it away because it looks funny or isn't there at a restaurant.
It looks funny because living organisms don't have a lot of clean, straight lines and are often squishy and lumpy. The restaurant removes it because it's too variable to cook without attention that's too expensive to give, it's too small for sale, or it simply messes up a clean presentation. So instead it gets quickly cooked and eaten by them, taken home by the chef, or added to soup or broth.

Being terrible at cooking and kitchen management cuts across economic lines.