No, S. boulardii IS a probiotic. It just is a probiotic yeast instead of a probiotic bacteria. I think you are getting hung up on the notion that S. boulardii is known to help keep C. difficile in check. In reality, the way ALL probiotics work is by keeping any one bacteria from proliferating. So, they all do the same thing, just in a slightly different way. Some probiotics will compete against some bacteria, and the thinking is that if you vary the probiotics, you are more likely to hit more targets.
We really don't know which probiotic we may individually be deficient in, but it is known that folks with IBD tend to have a reduced capacity to colonize probiotic bacteria. That is one theory of why we are more open to uncontrolled inflammation once we get infected. Since each person is different, there is no one-size-fits-all probiotic, just like everything else. Some get great results with one type, others have no effect or terrible gas. You just have to try and see. Plus, it is hard to prove a negative. "I took XYZ probiotic and hardly ever get pouchitis." Since there is not much clinical data (except for IBS treatment) it is hard to know if you'd also be fine without it.
Jan