Distributor's/Hardware catalogs are notoriously inaccurate and often did not reflect the factory catalogs. I have a feeling that many large companies like Shapleigh's, Tryon, Bekeart, Hartley, Folsom, Simmons, etc. had a staff of gunsmiths, engravers, and re-stocking craftsmen. If one can cut a barrel in their basement, how hard could it be to do it in the shops of the big hardware stores??
Chronology of barrel lengths are below from 50 years of S&W catalogs. Options and inventory kept dropping in the Twentieth Century
1887 - 38 Safety - 3 1/4", 4", 5", 6", 8", 10"
1901 - 32 Safety - 3", 3 1/4"
1901 - 38 Safety - 3 1/4", 4", 5", 6"
1903 - 32 Safety - 3", 3 1/4", 6"
1903 - 38 Safety - 3 1/4", 4", 5", 6"
1912 - 32 Safety - 3", 3 1/2"
1912 - 38 Safety - 3 1/4", 4", 6"
1916 - 32 Safety - 3"
1916 - 32 Safety - 3 1/4", 4", 5", 6"
1923 - 32 Safety - 3"
1923 - 32 Safety - 3 1/4", 4", 6"
1925 - 32 Safety - 3"
1925 - 32 Safety - 3 1/4", 4"
1931 - 32 Safety - 3"
1931 - 38 Safety - 3 1/4", 4"
1938 - 32 Safety - 2", 3"
1938 - 38 Safety - 2", 3 1/4", 4"
1941 - 38 Safety - 2"
We usually consider the offerings in the catalogs as standard production ordering options, with special orders sometimes filled by the factory. By the 1930s, I believe they were working off existing inventory and available parts, so the list of barrel lengths kept getting smaller up to WWII. Of course what they offer does not mean that there were many sold, just look at the 1887 offering of 8" and 10" barrels for the 38 Safety.