I'm not 777, but I asked a 777 bloke is it possible to hit the toga button and not get TOGA. He said no, the auto throttle will always give you TOGA. I said what if you have touched down? He said - "I don't know- I think so". He went and looked it up and said bugger him, he didn't know that that it might not advance the throttles if you had done a bounced landing.
He is very experienced on the 777 and said that that scenario, i.e. going around after a bounced landing, he has never practiced.
For once I think the airbus automation may be better for a go around (i.e. we always push the THRUST levers fully forward.
Caveat - I am in no way suggesting that this occurred in EK 521, but it does provide food for thought.