The beta acids also contribute to bittering. Some feel they add a smoother bittering (or maybe it was harsher...) but typically they are felt to add such a neglegable amount of bittering since they don't isomerize in the boil (or maybe they boiled off, I don't remember well, it's before 7 and I haven't had coffee yet). The Beersmith people probably added it in there expecting it to be one of the next things people care about.
鯰 a.k.a. なまず a.k.a. Catfish