I meant that the screws themselves hang loose. On a low-cost average receptacle, if you unscrew the screw it sticks out from the side. On spec grade devices, including most 20amp- when the screws are loosened, they dangle around. If you tilt the device upwards so you can see what you're doing, the screw head drops down.
Yes, they have the ability to be back wired. 99% of the time, I use the screw terminals.
