It is true that there is a tolerance associated with both minus and plus pins and there is no guaranty that a minus pin will measure in at nominal - .0002" or a plus pin at nominal + .0002".
I have to say though, I have never measured a pin that wasn't exactly .0002" under nominal for a minus pin or .0002" over for a plus pin based on a micrometer measurement. Just luck, I guess.
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In many instances, I just want to know if a hole is .250" rather than .249" or .251" and the tolerance band is good enough for that. For any critical dimensioning, I always measure the pin with a micrometer.
"Trust but verify."