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Every day's a school day!
FWIW, the limiting tension on a CrMo 5mm QR is about 9kN, which gives a normal load of about 4.5kN at the friction faces holding your wheel in place. Even a lower 8.8 grade nut on a solid M9×1 axle can be tightened to more than 20kN tension or 10kN normal load. Even better, instead of 108mm of 5mm rod being the spring in the middle which let's the dropouts bounce out of the sandwich, there is just 6 or 7mm of 7.3mm root diameter threaded rod on each side to stretch. For a given prying force, that's about 35 times more elastic displacement in the QR skewer compared with the short exposed piece of axle in a nut fastened set up.
gbj_tester-
Interestinger and interestinger!
I've often wondered if there is such a thing as an emergency QR for touring and expeditions that is long enough to use on a rear wheel, but that has a long enough thread to work on a front wheel. That way, if either QR snaps then it will get you to the next town; however that would only have a root diameter of just over 4mm along ~30mm of its length when used for the rear wheel, which would make it even less strong.
ffm
Every day's a school day!