I don't think its a round hole we want at all. Where we drill, the two sides of the hull aren't parallel. The through-hole will enter and exit at an angle. The resulting holes will be ellipses. Not to worry . When we cut the "doughnut" at an angle flush to the hull, we arrive at the same ellipses. The best analogy is a stovepipe through a roof; a round pipe fits an oval (elliptical) hole.
New standards for teaching high school math call for eliminating the study of subjects like conic sections. Future generations will wonder how we got those shapes to match perfectly.