Bill,
The more that I think about it, the more that I believe that Roy's comments accurately reflected the feelings at the Factory at the time the guns were made.
I have always considered the family tree of the large frame, fixed sight, under-barrel lug, hand ejector to be: Triple lock->Model 1926->Heavy Duty->Model 1950 Military . I think that chronologically, and in the S&W Design Department, that was true. However, over in the Marketing Department a different dynamic was developing.
Following World War I the Second Model .44 HE was satisfying the public's need for a large frame handgun. From the Factory's point of view, they were pleased because they were able to use up a large supply of leftover Model 1917 frames and that fit well with their "waste not, want not" philosophy. The only complainant seemed to be a small pawn shop down in Fort Worth Texas that kept yammering for a heavier barrel underlug to satisfy their colorful and vocal, but small market...the southwestern lawman. Finally, in 1926 the Factory acquiesced and made up a relatively small lot of guns for that market. But the market was limited and didn't warrant the additional work/expense to justify adding the additional barrel contour to the catalog.
Things would probably have rocked along like that for some time except for one thing...that prime mover of American industry reared its head...COMPETITION! Down the street old Sam's boys came out with a hot little number called the .38 Super that was rapidly getting the attention of lawmen on both sides of the Rio Grande.
Back over on Stockbridge Street the conversation probably went something like: "Whaddawedo?" The answer came back: "Don't we have some of those heavy lugged barrel .44's somewhere?" "How about if we drilled a smaller hole in the barrel and tried to push a pill as fast as that new Colt is going?" The result is history. The S&W .38 Super Police (aka Heavy Duty) took off like a rocket and the sales of the .38 caliber version of the M1911 flattened out like its trajectory. This, primarily because the public, both civilian and lawman, was more comfortable with the revolver and still thought of the pistol as a special purpose military sidearm.
The .38-44 Heavy Duty became the darling of lawmen everywhere and the M1926 was returned to the shadows where it languished as a special order item another 10 years before it ever made it to a catalogue.
(my suppositions only)
Bob