They are all made to SAAMI tolerances, meaning you'll find as much average difference between dies of the same brand as between brands.
I've heard this several times before, so I went to the saami.org website. They appear to have all of their standards listed there, but make no mention of reloading die standards. The only relevant standards are for cartridge and chamber dimensions, with tolerances.
I've heard of some users who have had custom guns made, and had a set of dies made from the same reamer that cut the chamber of their custom gun.
My question is this: If the brass cartridge expands upon firing to fit the chamber, and then springs back to a smaller size, how would a sizing die cut with the same reamer resize the fired case to be smaller than the chamber?
I can see where, with a tapered body, you could simply advance the cartridge further into the sizing die, and make it smaller. But wouldn't the shoulder be set back too far then? What about the neck, which is not tapered? How would you resize the neck down from the fired diameter to a size necessary for acceptable neck tension, if the sizing die has the same neck dimension as the chamber that fired it (and is already larger than the fired cartridge neck)?
Or am I missing something entirely?