Yes, I know why they have the extra rivets, just didn't know if there was an industry term.
The 1943 CBC has a notation of a photo of 187085, noted as, "light weight construction." It also has another notation: Description, Railway Mechanical Engineer, October, 1939--Description of earlier lot, Class B50-21, Railway Mechanical Engineer, April 1938. I hadn't noticed such information before. For a D&RGW auto car it notes that it was described in Railway Age, January 13, 1940 and Railway Mechanical Engineer in February, 1940.
It also has two pictures that are reversed - 186028 has a caption that says it is of low-alloy high-tensile steel but is a picture of 186028, a welded car, and there's a picture of 193464 with a caption that says, "Welded construction," although it's clearly not as it's a car with ACR. Oops.
My suspicion is, "light weight construction," and, "low-allow high-tensile steel," will be reflected in those articles since the lighter weight was the selling point, not the fact that there were additional intermediate stiffeners required. Time to read RP Cyc 31-32 again a little more closely...
Modeling the New Haven Railroad 1946-1954