Goku shows and explains the Genkidama
Whis ask him to charge it while in SSG.
Goku answers the SS state interferes with the energy gathering (cfr. Krilin's explanation in ToP) so he thought it works be the same in Super Saiyan God and Blue
Whis insists. Goku agrees.
Genkidama charges in an instant with much more energy than before.
Whis explains SSG is a godly state, so the nature reacts stronger to it.