Most repop roadster bodies use a real body for the male plug to make the female mold that the body is madeout of.
The tolerances stated will allow for the mold and body shrinkage that takes place with spray up FRP.
The wider widths are probably from a body manufacturer trying to make more room for driver/ rider by building wider cross pieces which wouldn't be that hard to do for a plug using original sides.
My original steel body is so deep in storage or I would join in the tape offerings.