Psyllium husk is awful. It turns into goo in your stomach and remains that way all the way through. Prebiotic fiber is completely different, dissolving easily in water. I simply do not believe that these two things are in any way dietarily comparable to each other. The advice ‘eat more fiber’ when translated from nutrition speak amounts to ‘eat more miscellaneous’. Both of these things are ‘miscellaneous’, so they’re characterized in the same way, even though they have nothing to do with each other.