This is correct and maybe there is a good reason why a two piece barrel can't have 1/2" added to either side instead 1" on the backside of the hub - don't know but cost would double at least so not much point. Pamp has a set of 3 piece style and spent a great deal of time and effort tracking down outer collars to get the stagger he wanted and they are gorgeous. No cutting necessary that way.
I'm refinishing a set of style 42 and wanted 9" for the rear but they are very rare and no doubt pricey - adding the 1" to the inside is an affordable option at $550 to do a pair but the lips would remain the same as the fronts and require 10mm spacers and new lugs. Still considering but probably stay with 8" at all four corners.