I know about spacers, and there is a link the manual in the first post. For 112.5 one should use 2.5mm spacers on each side with 68mm bb tube and no spacers with 73mm bb tube. For 116mm there should be 3.5mm on each side for 68mm tube and 1mm on each side for 73mm. In both cases, 68mm and 73mm, the difference is just one 1mm spacer on each side. It won't move the crank by 2.5mm and even by 1.75mm, it will only move it by 1mm!
Sorry my calculation was to show it wouldn't happen anyway and that their aim was probably something else.
1mm drive side 2.5mm non-drive side, it may well be 1.5 and 2.
Keeping to the shifting for the top group might have been more important, tolerances on the splines I would guess is much easier than the wide tolerances on a square taper that are aimed at.
It seems a bit like the jump from 107 to 110 in the square taper world when all but .5mm is on the non-drive side iirc.
If they where doing it fully it would be 112.5 and 117.5 like the 113 to 118 in low profile cranks.