1/2 a turn followed by 1/8 is 5/8, unless the direction of turn switches between the steps. What 'new' technique book, and for that matter, whose are you counting as the 'original'? There are lots of technique books, although none that I know of suggest anything quite so strange...
1-3 of a natural turn is usually described as commencing to turn on 1 (with body turn beginning through the use of CBM, but no significant turn in the feet), so RF moves fwd; followed by LF swinging fwd, then swivelling to complete 1/4 to R, the feet ending LF to side and with feet parallel; and then RF closes to LF as the turn is completed (1/8), making 3/8 overall, to end backing LOD. The rise pattern varies slightly, between dance styles (the natural turn being common to several), but you are 'up' on toes as the feet close, before lowering into the next step.