A travel trailer is supported at three points of more accurate if a duel axle 5 points. 4 points are the tires and the 5th is the tongue.
Tongue weight is the force that is exerted by the tongue when the trailer is in the same attitude as it would be when in tow (that is if it is nose down level or nose high). This would be with no WD system active.
The weights of these 5 points are important to know. All five gives the total weight of the trailer. The tongue weight divided by the total weight gives you the tongue weight percentage. The greater this number is, provided you do not exceed the TV capacities, the better the trailer will tow.
The tire weights are important to make sure the tires and axles are within their ratings.
Thus tongue weight has nothing to do with a WD system.