correct John.
the difference being .031 in hole size vs bolt diameter allows for proper fit during assembly.
depending on a "super precise" item, it's possible to tighten up the hole size some, but you better be RIGHT on the money, within a few .0001 [that's ten thousandths of an inch] of the hole locations of both the [item with the] holes and [the item with] the threads to be able to assemble without the bolts either rubbing on the hole sides or the threads being deformed by the bolt not going in straight.
in the machinist world, you can't insert a precision 5/16" diameter plug in a precision 5/16" hole. [try it sometime. it won't fit without "pressing" it in.]