This is not that different to other incidents where the gear up was called for and the flaps were raised instead. It all boils down to the age old communication problem of what was said being different to what was percieved. Mandating use of the interphone I think would help mitigate that problem. A jet cockpit is still a noisy work environment and as both pilots are looking out the front, the other cues that help a person decipher what is being said by the other person are not present. At least using the interphone what is being said is heard in the headset and not a distorted bunch of words coming from the other side of the cockpit.
I would imagine that the Training Captain got a nasty shock when the nose started coming up in response to his "Go..TOGA" command.