I can't believe that you as a controller would be happy with issuing an instruction for an arriving flight to "go-arround not below 400ft" and that flight descended below that.
As an examminer, not complying with the instruction would be a failure point and I would have to intervene to ensure the safety (and legality) of the flight.
Similarly, manoeuvering the aircraft off the missed approach (either published or issued by ATC) would also be a failure point for very important safety reasons.
Regards,
DFC