Is the DC-DC converter on the Zoe permanently connected to the traction battery ? Unless it's physically mounted inside the battery enclosure with only 12v coming out it would be highly unusual to have live HV coming out of the pack for an external DC-DC converter even when the contactors are open as this would be a safety issue since you couldn't safely disconnect the battery. I can't think of any other EV's which do this.
If the DC-DC converter is external to the pack and runs through the contactors as it does in most EV's then there should be nothing inside the pack to draw a large surge current when the link plug is inserted during maintenance.
It's highly unlikely there is a large capacitor connected across the pack inside the battery enclosure before the contactors - one obvious reason is that the current drawn to charge that capacitor would still be enough to electrocute you should you touch between the two pins in the safety plug. Not much of a safety plug in that case.
With no capacitor (or other load) just the series string of cells and open contactors (12v battery disconnected so no way to activate them) you could in theory touch across the pins of the link plug socket without issue, although I don't recommend it of course.
Normally any filter capacitor is external to the pack in the motor controller unit and is not charged until the contactors close. In fact there is a dedicated pre-charge contactor which switches a resistor in to charge the capacitor at a controlled rate before another contactor makes a direct connection. (This also lets the car detect shorts on the external HV bus before it "throws the switch" and fully connects the battery to the external circuit, avoiding spectacular fireworks if there was an external fault)
Since the filter capacitor is there to provide a low impedance at the high inverter switching frequencies there is no good reason for it to be in the pack instead of the MCU as it will not perform its function as well at the other end of the HV cables, and there is no reason I can think of to put any capacitor inside the pack due to the safety issue with the link plug.
So I'm highly sceptical that there is any way this charring has occurred when the plug has been removed or inserted (since there should be no current being drawn)
unless someone pulled the plug while the car was fully switched on, against all good practice.
That's a pretty big "splat" to have occurred on just one occasion of the plug being pulled or inserted.
I'll qualify everything I've said as generalisations about how EV's are usually designed - I don't have any specific knowledge of the high voltage system in the Zoe but I have dismantled and worked on the traction battery in a Peugeot Ion and there is definitely no capacitor in the pack on that car, just the pre-charge resistor and the contactors. The filter capacitor is in the MCU.