The answer is very simple. They have access to powders and wads you don't. They even have a ballistics lab to use to work up safe loads. Wouldn't that be nice?
I've never hunted pheasant in Sowdakoda, but having lived almost all my life in Nebraska I have a tad bit of experience with shooting pheasants. Are they different in Sowdakoda?? I've never seen any need for anything other than a good 1-1/4 oz of #5s at about 1330 fps. The old 3-3/4 dram MAX load does wonders out of the business end of my ol'e Model 12!
I suppose IF I was going to spend real money and go on a real pheasant hunt I'd get all the gun and shell I could afford, but when they are just out the back door....
That said, over the years, and especially when I was still young, good eyes and reflexes, I killed a ton of roosters with the old Super-X and Remington Express 1-1/4 oz #5 loads. Waaaay out there too, so much so that at times it even amazed me. I don't believe you NEED any hot shot Golden Pheasant loads or any of that, but I doubt it will hurt anything but your shoulder either.