This is basically correct.
The full name for the part is hammer pivot stud. on prewar guns and the earliest postwar models, the stud was threaded into the frame on the gun's left side. What you are seeing is the end of the stud. This was replaced with a pressed-in stud, and on those, the stud end was polished flush with the frame. You can usually see it on close inspection, but it is largely invisible.
I'm not an N frame collector, so '49-'50 may well be correct on those. On the K frames it happened a bit earlier. The change order was issued on January 18, 1946, and was implemented very quickly. K frame guns shipped as early as April, 1946, had the pressed stud. The "High Speed" hammer wasn't used on fixed sight K frames until 1948. It showed up a bit earlier on the target sight K frame revolvers.