Very interesting observation. I can't recall any other particular dependence on Weymouth in the NWT off the top of my head.
But it seems possible this is the source of the phrase since Franz was eclectic in the places he gathered NWT idiosyncrasies. When I've got time I'm going to look at WT literature from the 1940s and 1950s to look for references to Weymouth, explanations of this "system of things" phrase, and the background of NWT peculiarities generally.