This is another example of there being no one right answer for everyone.
It is more common for j-pouchers to have problems reducing diarrhea, and one strategy is to avoid drinking much fluids with your meals, and hydrate well between meals.
If you have problems with frequent obstructions (not common) and these are food related (even less common), then drinking fluids with meals makes sense. Some people are even restricted to a liquid diet only. But this is rare.
So, I would focus on the typical, not the rare, and deal with things if they occur. You cannot prevent obstructions by drinking. They are more about your gut kinking, not because the food is too dry to pass. Of course, don't swallow your food without chewing!
Jan