Yeah, the catalogs didn't always line up with what was out there. In the 1971 catalog, the Down Beat and Rock Duo kits have 14x20 BDs, both according to the descriptions and the pictures (16 lugs instead of 20). In the 1973 catalog, the Down Beat set isn't even available, and even though they used the same picture of the Rock Duo set (with 16 lug 20" BDs), the description says 14x22s.
When I was a kid and drooling over the idea of owning a Ludwig kit, it seemed like what most music stores stocked was kits with 20" BDs, 'cause I saw a lot of them. In my memory anyway, I don't recall the 22" BDs being the norm until well into the early 70s. I suppose that might me just me, 'cause I had a 20" (Gretsch set) and badly wanted a Ludwig set with a 22. That was what was "cool." :)
So, special order or not, this sounds like a very legit, very good kit!
Bill