This story leaves out an important underwear development that’s more than a decade old — the horizontal fly. The thing is, for a lot of guys, that sideways flap was never very convenient. You have to start on one side, tuck your hand inside, move it all the way over the other side, fold back a flap of fabric, then reach back toward the middle. It’s a little easier for the guy who sticks straight out, but for bigger guys who hang down, it’s like a torture chamber strangling the neck of the guy down under. The horizontal fly changed that. It’s just a quick slip of the hand in and pull up. Much easier. Not unlike the over the flap method, but it doesn’t require unbuckling or unbuttoning the pants.
As for sex through the hole, sexy is in the eye of the beholder. For an uncut guy with a loose foreskin, there can be an added benefit of the underwear pulling back on the testicles to help keep the foreskin retracted without the potential pain and injury of a cockring. Leaving the underwear on can also contribute to an “in the moment” feeling. It’s probably not something a guy wants to do all the time, but for a change of pace, why not?