Here was the technical explanation of it. But more surface area on the suit in ski jumping means more air time. Especially in the crotch region (no joke). A few cm of extra fabric there would be a few extra feet of extra distance for the jump. Due to the strict guidelines I guess a bigger Flaccid would mean more space allowed for the suit which would mean a lower inseam or more fabric to create wing when your legs are spread apart.
Now that this story has gained so much traction it's a bit too late for the athletes to do this in time to compete for the Olympics. But I remember seeing that the Olympics Committee doesn't plan on examining athletes for this in the future for anti doping. I guess it would be too hard to detect... Pun*