Why did the scutum have a horizontal grip?

[QVINTVS ARTORIVS CORVINVS]

Actually as a veteran Martial artist and student of human movement, your radius and ulna are only in straight alignment when your hands are at the figurative position of 10 & 2 like when you put them on a steering wheel. That said, whenever you punch if your bones are in a state of torsion, there is a danger inherent there. Straight bones = the greatest/safest transition of energy. So in actuality, the ideal anatomical placement of the scutum handle would be at about 55 degrees or so. This would allow the stronger shoulder muscles to more effortlessly hike the shield up if necessary, afford a much stronger punching angle and still be very comfortable on the march.