1...g6 was more solid, when White could try 2.Qh6 Bf8 3.Qh3 followed by Ne4, eyeing the new weakness on f6.
As a result of Black's first move, 5...g6? now fails to 6.Bxg6 fxg6 7.Qxg6.
Provoking e3-e4 in order to restrict the bishop on g2 and gain control of the dark squares.