Thanks. I guess that became necessary when they decided the fight should pause whenever a charge attack is initiated, to allow players to tap their screens to affect how much charge is in the throw or in the defensive shield against it.
I prefer the immediate attack when the trainer hits the button, as it does (more or less) in normal gym fights. The pause to attack feels too contrived. (On the other hand, it IS sort of consistent with the way the pokemon target circle stops shrinking the instant the trainer throws a ball.)