Maybe codes specify now, but in the olden days the ground up or down was argued endlessly like the great toilet tissue over or under debate. I have an older GFCI in a basement bath that has the instructions molded in to be readable for either installation orientation.
If the duplex outlet is installed ground pin down, the ground pin tends to resist the downward force of gravity on cords better than the current-carrying blades but is also more susceptible to bending and breaking off in that position. The hospital code clearly recognizes that the ground pin is not a device designed to prevent those pesky cords from unplugging themselves. The mech for that is the twistloc design. I like the close quarters plugs seen often on refrigerators.