As you can see from the title of the picture it says “approximate”. We are talking a difference of 2 to 3 mm tops with the size of rivets, edge vs. center measurement. I would imagine as long as you’re consistent - e.g. keeping your rivets on the same plane, not crooked or at a diagonal - I do not see the DO’s denying EI/Centurion because your rivets are 2mm “off”.
AFAIK no-one has taken calipers to a film used suit anyway, so the best we have is approximate.