I agree, KYDan's cutter is made same as the standard duty in the video. Why they would market the same design for standard and medium or heavy makes no sense unless they're just using thicker metals (based on his damage photos it doesn't appear to be the case). Although if you look at that area on the other brands in the video, I don't know that the Kodiak design is much worse off than any of the others, but perhaps it could be a softer grade of steel.
I still think the video gives a lot of first time shoppers some things to look at and consider. I know I've ran at least a dozen different cutters in my life, but never had to buy one and when it came time to buy one they all looked pretty-much the same. Hitch designs are just one of the things it points at to be looked at. (for better or worse)
With a tractor that size, and a stump of 4", I'd have to wonder what wouldn't have bent in the exact same circumstances before calling a design bad. Perhaps it was just a bad choice for the tractor and terrain as both that tractor and the 4" stump are a bit much for any standard duty design. They shouldn't be marketing the same stuff for various duty levels...