Hi Tee Emm,
From the FCTM:
"At typical landing weights, actual thrust required for a normal go-around is
usually considerably less than maximum go-around thrust. This provides a thrust
margin for windshear or other situations requiring maximum thrust. If full thrust
is desired after thrust for the nominal climb rate has been established, press
TO/GA a second time."
As for the thrust setting during a manual go-around. In our company we do not need to set maximum go-around thrust with both engines operating. Only a single engine go-around requires us to set maximum thrust. Maybe it's a company thing?