It seems to me it's only an opinion of a few owners on here that state "they" don't need it. For me after riding one with stock and 6 people on board the very first thing I would do is add 750's to the back and atleast 500 to the front, and I am far from being a pro, but love having fun on a big fat wake! But before I'd buy it I'd try and get a ride on one loaded like so to make sure it can hold its shape when loaded.
Maybe the OP should post this on Wakeworld also. Might be members there who have rode on a loaded x-25.