Where did the 30mm hit in this case? There has to be one way or other to remove any doubt that the 30mm caused registered damage but didn't do (what we're considering) normal damage, i.e. a wing off, or an engine kill, or a pk depending on where it landed. The only fuzzy aspect I expect is some planes only getting oil leaks from a tater in the engine (tough ones like the 47 or hogs), or non-fatal rudder/vstab damage on hits to one side of the tail (in the 38 or 110).
Unless someone can say they've always had planes take these hits and shrug it off more than once every 50 times, since 2000 or so. I know that in my experience this apparent fluke has only been going on for the last 3-4 years or so. A tater to the engine before then would always kill it instantly, and a hit anywhere in the wing would at best break the wingtip, and at worst take the whole wing off. I have never seen first hand an oil leak that takes only a few seconds to run out.