Lets say I have maim wings on an opponent's flying creature, unrevealed.
My opponent activates the creature.
At this point, if I reveal, my opponent will not be able to target a flying creature.
Lets say I wait until my opponent declares the attack, and targets one of my flying creatures.
If I reveal now, since the target has already been declared, I would expect it to be too late to prevent the attack.
Thematically this would represent maiming the wings after the creature was already locked in combat with the opponent, so it is too late to negate the target.
Does this sound right?