I’m not an electrical engineer, but I think it really does depend on the implementation of the PCB. From my understanding, connecting a conductive plate and case to USB shield will significantly hinder the ability of a transient to reach sensitive components along any shared connections (people usually just tie shield to ground or leave it isolated), but, if the reports are true, the voltage may reach the circuit regardless. Additionally, the damage to the components may have occurred through some other means that is less obvious (a short elsewhere on the PCB, bad cables, power management issues, etc.). Are you sure ESD is the culprit?
In short, while ESD chips do function by diverting excess electrical energy to ground in line with your logic, there is no such shortcut to arrive at protection. The design of the board itself needs to account for transients.