I have a 4" Model 14-3 that lettered to July 1971. It was shipped to Dave's House of Guns in Dallas. It did indeed come from the factory with a 4"barrel.
Speculation is that every once in a while, S&W would turn out a batch of maybe 100 or so in this configuration just to test the market.
While they are scarce and unusual, they do happen. I've never noticed any particular special interest or value attached to these guns. They may bring a little more than a Model 15, but it won't be much.