-
is the torsion always too great over such a long and thin bolt?
That's the issue. A cam operated skewer only has to resist tension, where the Allen key one has to simultaneously resist both the tightening torque and tension. It's not to do with the length, although in practice the wind-up of such a long bolt causes the same problem as uncorrected spoke wind-up. In general, the tensile yield limit of any threaded fastener is greater than the tension which can be generated by fastening, because the thread snaps at the first unengaged turn under the combined loading.
Any data on the QR vs hex skewer claim?
I’d have thought that a properly-lubricated Cr-Mo hex skewer has the potential for greater clamping force than a hand-applied closed-cam QR... Or is the torsion always too great over such a long and thin bolt?