Not only that, but if the attack comes on the center, for you to intercept it with say paak or taan, or to wedge, or whatever you guys use, you have to first move your wu to one side or the other and come back at center, or step to move yourself to one side or the other.
Both options, as I said, are not as direct or efficient as having a wu in position ready to go, and there will likely be little to no time to decide and respond correctly.
In the YM VT I train, we keep the wu sau on-center and a good distance in front of the chest. When an attack comes in, we meet it by going forward on centerline, with the intent to hit, not to block, using the wedging principle to simultaneously deflect the incoming attack. We only resort to tan, pack or bong if the punch obstructs our counterattack and we have no alternative. Keeping the wu-sau to one side may be helpful, but as you never know exactly how your opponent's punch will come in ...what angle, on center or slightly off-center, etc. we do not see keeping the wu of-center as a solution.