Hi Jeff,
You say: "...the PCB house ... may opt to alter the drill size based on 
several factors -size, geometry, aspect ratio, etc."
This assumes, that the PCB house knows something about the operational use of 
these PCBs—rarely the case, or that it knows more than the designer what is 
needed—too often the case.
However, for knowledgeable designers that design a high-reliability product, 
particularly for severe operational environments, and who know the 
capabilities of the PCB house, it is much better to specify the drilled hole diameter—
again all too often not the case.

Werner

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