I have not figured out how to open a new thread here - strange
You have tried to post under FAQ section, but it's not possible to create new topics here. And your custom question is not related to FAQ at all; which means... it is not amongst Frequently Asked Questions at all.
So far I could only tell you $viewTopicsIfOnlyOneForum setting is designed for community where only one forum is present. When this setting is on, only one forum having top order number will be displayed - always.
For making the thing you want to achieve you probably will need to apply some additional hack/code... but I suppose this is custom question and I can't answer precisely what needs to be done.