Currently (3.3.2) the "Center on opponent's move" feature does not really center on the moved unit. Rather it makes sure the hex where the unit is moved to is visible in the player's screen. In the situation where the move occurred outside of the area the player was seeing before the opponent move, this results in observing the opponent's move on one of the edges of the new visible area of the map.
This feature will be more effective if the opponents move is placed at the center.
Technically this should be feasible and might have been overlooked when this feature was initially developed.
There is already some code to recenter the map on a right click (see VASSAL.build.module.map.MapCenterer)