The rule about WC is intended for managers.
When I am the manager, I am strained with complex bureaucratic rules of granting WC. I cannot understand, why cannot simply write
Also should write
The offered variations release the manager from extra work.
this is not bureaucratic at all, this is giving the player a choice whether or not s/he wants to play using 1 of her/his WCs. Sometimes players post picks thinking they have committed to this tournament. When you tell them they should be a WC they have to be free to choose. What you suggest means you as a manager decide for them that they have to use 1 of their WCs. What happens if someone doesn't want to waste a WC on a 250 tournament? Picks are posted, WC is granted automatically -> WC is counted used. No going back.
IMO it is not for the manager to decide when the players should use their WCs. I have had players who once they learned they'll need to play as WC they just didn't play, probably keeping their WCs for bigger tournaments.
I am against your suggestion because it deprives the players from choice. IMO players have to state clearly they want to spend 1 of their WCs on that specific tournament.