Bob,

Maybe you can clarify what is driving your question.  You state that the ±.016" seems liberal (and I agree) but this is our subjective opinion. Are you asking from a design/OEM perspective or manufacturing/supplier perspective? Section 3.4 of IPC-6012 states the printed board shall meet the dimensional requirements specified in the procurement documentation. However, if there truly isn't any requirement specified then you default to the applicable design series specifications. I would think it is very rare for a drawing to have no requirements, to not even have the "Unless Otherwise Specified" title block tolerances on sheet 1, which typically default to something along the values of three place decimals ±.005", two-place decimals ±.010".

From a design perspective, IPC-2222A, paragraph 5.4.1 states the tolerances specified on the drawing shall accommodate the dimensions and tolerances of the mating part.

I suggest clarifying the requirement before manufacturing product.

Regards,
Scott