It absolutely has changed. His swing change increased his batspeed and changed his swing path, 2 things that can definitely lead to more max distance.
Fly ball distance is basically determined by (in terms of what the hitter controls): Speed of bat, weight of bat, backspin, launch angle and to a smaller extent wrist strength (the less give on the bat on contact with the ball the better). A swing change directly effects 3 of these (speed of bat, backspin and launch angle).