Rear Shock Orientation.. Aftermarket vs. OE

Hey guys,

As I'm looking at photos, I've noticed that the OE 4Runner rear shocks have the shaft at the top, and body at the bottom. However my aftermarket Eibach rear shocks have the shaft at the bottom, body at the top

Does this have something to do with mono-tube vs. twin-tube? I suppose I could see why a twin-tube shock could not be inverted.. or maybe I'm making that up in my head.

But why has the aftermarket inverted the shocks? Is there any downside to inverting the rear shock? It seems like the shock shaft is its most fragile part.. so I'd think placing it up at the top would be preferred, no?

Do any aftermarket 4Runner rear shocks place the shaft at the top, body at bottom?

Thanks!