@Aguila Blanca: My GI Expert was made before any EGW extractors were used. Originally, EGW extractors were used to replace faulty "power extractors." I don't know what models currently use EGW extractors. If many models do, I'm curious if that is due to the Para ones not being up to par. I don't know.
The tolerances you mention are after the CNC machine is setup. If there is a mistake with setup, then things will be out of spec, though all products worked on will be within the same spec (I think).
The issue that makes me wonder if mine is within spec or relative spec, for lack of a better term, are failures to feed with conservative ball ammo using the new OEM Mec-Gar mags.
There are variances between firearm models with the same barrel lengths just like a 5" Kimber will have tighter groups than a 5" RIA (not a fan of Kimber).