In the UK, that bare wire would have to be sleeved inside the box with green-and-yellow sleeving, and should connect to the outlet first, with a separate sleeved wire from the outlet earth terminal to the metal box (if the fixing screws don't perform that function). However, using an NM clamp to terminate them is wrong. Except in this case, this. However, in actual applications, distribution boxes often encounter a series of problems, which not only affect the normal operation of the power system, but also may bring safety hazards. The bare ground wires should be terminated at a second termination bar that is bonded to the distribution panel which in your picture does not exsist. The feed wires from the main. The EGC for the NM has been cut back and wrapped around the sheathing outside of the service panel.
[PDF Version]