You were free to order any combination of drums you wanted. The catalog sets were merely suggested setups. I'd suspect that someone wanted a Downbeat set but with a bit of added oomph that a 16" floor would offer over a 14" so they ordered it that way...or maybe the music store sold the 14" off to another customer and then replaced it with a 16"...or someone bought a set without a floor tom (a common way to make a set more affordable back then) and then added one later, opting for a 16" (or simply a matching 16" was more readily available). No way of ever really knowing but my point is there is no reason to think less of a set of drums simply because it doesn't match up to the handful of suggested setups shown in the catalog(s).
The drums were all the same regardless, the cataloged sets were merely different combinations of those same drums and the 8x12 tom in a Downbeat was identical (and interchangeable) with one from a Hollywood setup or any setup someone could think of that included a 12" tom.
Drum buying was more like car buying back then, you could take one right off the showroom floor (usually a catalog configuration) or you could order one up exactly how you wanted it, with different combinations of drums, different (or extra) spurs, double mufflers, etc. etc. The options were there for the asking.
Incidentally, while a 12/16/20 prepack combo did not appear in Ludwig's catalog that was a reasonably common configuration with other manufacturers, particularly Rogers, who seemed to favor the 16" floor tom as their standard size in most sets. So the idea was certainly out there and someone may have seen that in a Rogers catalog and thought that was the combination they preferred, even though they wanted (or could only afford) a Ludwig set.
