nd how about for a GA, push TOGA and give it a full arm of thrust, does that cause any issues?
There are two issues. If you are flying a manual throttle approach and decide to go-around the only reason you press the TOGA switch is to bring up the FD needles to their GA attitude. Most pilots should be able to perform a perfectly safe hand flown go-around without the urgent need for FD guidance. However, other pilots are so reliant on automatics that a GA without FD guidance is almost akin to a Mayday. The Turkish Airlines B737 crash at Amsterdam was inevitable when the crew seemed mesmerised by the fact the throttles did not appear to work automatically.
If the auto throttle system is operating during an instrument approach, then commonsense would assume you guard the throttles and when TOGA is pressed and instant opening of the throttles did not occur , you would quickly set them at the go-around setting.