Yes that could be one way to describe it. I suppose a model like this would only be applicable to forums who’s subcategories per categories are identical though now that I think about it. Then again cases like these are pretty common.
Like for the support forums idea, in the traditional forum layout this would have all the products as main categories, then every category would have the same support type divisions as subcategories.
For the gaming community I had in mind, we’d have all the relevant games (and general) as the main categories and every category would have the same subcategories. Namely; general, gameplay, help, usercontent, tournaments and events.
It’s very possible to have people who just want to browse all the usercontents for every game, or maybe the tournaments going on for every game (since this is a specific gaming community, the games are pretty similar in mechanics). Being able to filter using only the 2nd list of categories seems like a real plus to me.