I have no idea who was the first to ever fire a break open double with the bolts removed, "BUT" both W W Gereener & D M Lefever stated it as fact long before Win was making a 21 or Browning was making a Super. I don't have a 21 at hand to measure, but I believe the bar on a Lefever is equally as long, if not longer. The 21 of course has absolutely nothing in its design to contain the axial thrust except the hinge pin. The Lefever design assisted it with his square shouldered Doll's Head, with the bolt at the top to also help resist frame bending.
One Shoe don't fit every foot when you go talking gun design.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra