I agree with the GMs.
Whereas many common lines are in the progress of being boiled down to drawish endgame positions with the aid of computers, playing g4 at some point during the opening unbalances the position immediately and announces White's ambition to attack Black's kingside. Also, many players do not expect to see the move g4 early in the game. I believe it's an effective way to utilize the advantage of the first move, as long as you're prepared to deal with the outcome.
During Round 1 Shahade and Ashley mentioned that g4 is the new "hip and
trendy" move. In fact, I believe there were at least 3 games in which it was
played. They said white is willing to play the move anytime at all.
Why is this such a hot trend? What is so great about g4 as a move? If
white has castled kingside isn't g4 too risky a move?