Inzer Groove Briefs and the Ensuing Agony

I just ordered a pair of groove briefs, allegedly one size too big according to their size chart. I was wondering if you’re supposed to pull the bottom of each leg up to the crease between your leg and hip (making them look more like underwear than boxers)? That’s the impression I was under, but when I try to get into a sumo position, the pressure on the sides of my legs prevents me from setting up properly; I feel like I can’t really push my knees out. I know they’re supposed to be tight, but maybe I’m doing something wrong.

Thanks in advance for the help.