The apocryphal historic reason was that before modern riichi mahjong, there were many things that were not part of the game. The base exponent (bazoro) was not included, and points were rounded to tens, not hundreds. There's a style of play that can be called "22-style" (aru-shii-aru) in which the minimum value of a winning hand was 22 points. However, as we know, if a hand has at least one run exposed, a valueless pair, no sets and finishes the last run with an open-ended wait, the hand would score no points aside from the base score (fuutei). So it was decided that an "open pinfu" hand would score 2 points in order to not have valueless hands. There was some doubling, but I am not an authority on what they were, and how different they were from modern yaku, both in scoring and in presence/absence.
Scott Miller did do some research down this field and most likely contacted people from the 101 Competitive League (http://www.101fed.com/). They still play with rules faithfully matching how mahjong was most likely played in Japan in the 1930s and 1940s. However, during and following WW2, the game evolved considerably. As modern riichi mahjong became what it was, the old style got left behind. The 101CL now has a grand total of 18 regular members in 2016 (from a peak of 45 or so in the 1990s), showcasing exactly how unpopular the old rules were to become over time (for fair comparison: JPML has around 650 and Saikouisen NPM has about 400, and there are other pro organizations).
Because of this transition, attempting to catalogue what japanese mahjong was in the sixties was done extremely poorly in a 1964 book whose author I do not care for (E.N. Whitney?), because of the overlapping explanation of old style, modern style, as well as some rules that were still in flux somewhere between. Her paragraphs on furiten are comically imprecise precisely due to this transition. My recommendation to NJ players is to ignore any written reference prior to 1980, as it does no one any good to dwell on the specifics of ancient practices, and not to revive apocryphal yaku from that era.