For example, the Galfan coating (chrome plating) covers not just three hundredths, but just fills almost half of the thread profile.
It is necessary to remember the rule that all dimensions in the drawing are given taking into account the coverage. And no excuses here do not work, we then covered according to your size, and the screw and nut for some reason do not wrap, although the deviations to the coating met the standards.
For threads with protective thin coatings, such as galvanic, tolerances and limit deviations are applied to the dimensions of the parts before coating.