I stopped piecing together my sets by packs and singles in 1971 and after that just bought sets, so no expertise on the underlying question. It has always been my impression that Topps did "issue" the cards in series, at least in most places. But that would not mean Topps did not issue them all at once in certain locals, since I think Todd is right that the set may have all been produced at one time. Since Topps clearly went to full distribution in 1974, maybe they were testing the different distribution method in some areas
As Todd mentioned Topps often tested and experimented with new ideas on a regional or geographic basis. In 1973, in addition to its base set Topps tried out
Candy Lids, Comics, Pin Ups, the Team Checklists and the 53 Reprints ( although the latter may have just been an item created for a function or Banquet).
