They weren’t called that, were they? Usenet was just Usenet, or “news.” BBSes were BBSes.

And in context, “forums” was presented opposite plain text, and pre-web stuff tended to be plain text.

They were still forums. And there were some graphical usenet clients that were arguably better than any web forum - 35 years latter and much better graphics toolkits exist today. similiarly, not all bbses were text basee, though with modem being so slow that was the default.