From experience they are correct! High Brass 6 Shot is the besty way to go. Whether shooting a 20 ga or a 12 ga. And if you are not always shooting over dogs (setters or close flushing spaniels like springer spaniels who work very close normally) in very cold weather when the birds a holdong very tight, anything else under High Brass 6's are going to allow the Feathers to Fly the Meat Away!
as us old bird hunters refer to it.
I hunted over dogs for years (with English Setters & Labs) for pheasant and quail and used a 20 ga. to hunt them with so not to damage anymore meat than I had too. And especialy with a flush close to my location. Sure miss it now living in Tennessee! We do not have pheasants and few quail here other than some put and take farms.