Let's talk about trucks

For the record, I mount and balance my own tires on all 6 of my vehicles except my wife's 2020 hyundai (actually I've done one of those, too).
I buy my tires from ebay or tirerack.com, and have them shipped to my home and I've never had that issue.
I have seen slight differences between different manufacturers. You'd think they'd all use the same size "mm" to measure with.

I believe part of the issue stems from the width measurement being "section" width, which is the soft area of the sidewall. Obviously, this can be affected by variables like air pressure, if in fact they are measured mounted.