It's just guidance on a way to allow the vagus nerve, Leptin, and GLP-1 to do do their job. If you eat too fast you can overeat easily. It doesn't allow these peptides and hormone precusors to do their job. It's not the chewing but the saliva production that helps this process. The "chew for a minute" heuristic is just to allow enough saliva production to ease digestion of rougher and less bioavailable foods. Anyway, the human body is wild.