"Force users to accept the rules for a forum before they can view the forum." bought the product for this reason. But you can't actually force them to accept before viewing the forum itself. Instead it's each node. If you're looking for something that'll stop the whole forum from being viewed this isn't the product you're looking for.
The resource listing is very clear in the features offered. We repeat that the add-on allows you to configure "per-forum rules", the screenshots all only show specific forums having rules attached to them and are unambiguous in this regard. Indeed, the statement you've quoted also indicates the same. The 'forums' are the individual forums, and the board is the XenForo installation itself, and this is the same terminology used throughout XenForo's options. We've left no ambiguity in the resource listing or the screenshots, and made no suggestion that the add-on will force users to accept rules before viewing the board itself. We encourage all potential customers to contact us with pre-sales questions, either in the thread or via our support link.