Well, they sure as hell never made one stamped "Old Model"!
You may as well lump that with the people crying about calling it the ".45 Long Colt" and Jeff Cooper having a hissy over calling a revolver a pistol; it's just semantics used to attempt to intimidate the new guys with your "superior" knowledge base on one subject.
Nope they didn't mark them "Old Model". However, when they changed the action to the New Model design, they kept the names (Blackhawk, Super Blackhawk, Bearcat, Single Six) so to differentiate between the two action designs. The manufacturer initiated this designation. Years later, Ruger introduced the Vaquero, a New Model single action in design. That model was removed from the catalog and replaced with the slightly smaller model designated, again by the manufacturer, as the New Vaquero. Says so right on the cylinder frame "New Vaquero". It too uses the New Model action design just as they all have since the change. Hmmm, all these designations were given to their respectful models by the company that produced them. So sorry but it's not as you say,
"semantics used to attempt to intimidate the new guys". It's simply properly name usage. No different than someone simply deciding to call a person by a wrong name.
As for the whole 45 Long Colt thing...in ways it's wrong but it's become to mainstream with ammunition companies using that terminology it's become accepted throughout the industry. There were 2 different cartidiges with this same designation. One is as we have today known as the .45 LC. The other was a shorter version of the other cartridge named the .45 Colt as it was known. Can't have two different cartridges with the same name so one became the "long" Colt.
Not "superior knowledge" either. It's again, simply knowning the proper terminology. Some can take it as what it was intended originally, good humored and to let someone know thier terminology wasn't correct. Some others...well, they simply are so sure that it's exactly, 100% as they say it is:
it's just semantics used to attempt to intimidate the new guys with your "superior" knowledge base on one subject.