There is nothing in NEC code that says the ground has to be installed up or down. The AHJ (Authority having Jurisdiction) in a state can require it to be up or down. In new construction the electrical section in the spec book can require the grounds to be up or down. A hospital project manager can just say one day I want them up.
For years the majority of outlets installed in my area in Hospitals and Healthcare Facilities were down.
The paper clip one was used for the reason in hospitals and healthcare facilities in my area. Story goes, a desk against a wall. Outlet below desk. A paper clip is knocked off from the back of the desk. A cord and plug is not tightly plugged all the way into the outlet. Paper clip falls and lands across the Hot and Neutral blades of the plug. Result, fireworks... What are the odds???
@erik_squires explanation is more the reasoning for the ground up. The stainless steel plate falls off and lands, in most cases, on the plug body and that's where it sets until,... But sometimes if the plug is out a little bit it hits the plug blades. Fireworks!!! Breaker trips right? Not always.
As for the 6/32 trim screw that holds on the plate working loose ??? Well the problem, it was not tight. Not even snug. Whose to blame? The Painter.
The painter? The painter pulls the plates and is responsible to put them back on.