Interestingly, the first edition of Alex Moore's "Ballroom Dancing" also from 1936 appears to be subtly different, it says "Amount of turn. Make one-third of a turn on each three steps ". This was not changed to 3/8 until the 6th edition in 1951.
As Telemark says the amount of turn is described over each _group_ of three steps, not per step, so the total turn would have been 2/3, later changed to the 3/4 that we need to adhere strictly to the diagonals as now defined.
When reading Moore's technique it is important to read everything, preferably several times. He discusses inside and outside of turns in the General Note of the Natural Turn as man, and says: "For the same reason, the continuance of the turn on the ball of the foot on the 2nd step of the forward turn is much more marked than in the backward turn."
Finally, Moore's footprint diagrams generally make things very clear, particularly in showing any turn on the standing foot as the next step is taken. As the saying goes, a picture is worth a thousand words.