Among the early K-Frames was the K- series Masterpiece target revolvers. I personally preferred a muzzle heavy revolver, as I think most did at the time, I still do. The square butt allowed the beefy heel of the hand to better support weight out front in bullseye shooting, as well as for field shots with magnum revovlers.
The smaller round butt blends under a coat or jacket better without "printing" and giving away its presence.
I had some correspondence years ago with Smith & Wesson, and simply put, round butted guns sold better, so the decision was made to go to round butts on N-frames as well. And, stocks could be made to convert the round butt to a square butt configuration.
That's my take on it.
Bob Wright