I thought the shock could be positioned so that there is less unsprung mass (ie the heavier end of the shock isn’t having to move about)
I can’t quite work out whether the shock body/dial end is heavier than the shaft with other internals in or not
The weight of rear tyre, (tube,) rimstrip, rim, nipples, spokes, hub, skewer/axle, rear stays/swingarm/rocker, brake caliper, rotor, rear mech, casette and partially the chain, brake hose, gear cable inner/outer, bearings, bolts and so on will presumably dwarf any difference in weight between shock orientation hence so noticable difference?
Unless having the damping oil/cicuitary largely still or being moved with the bumps makes a difference?