You mean the assumption that all the text in the rulebook is rules text? I’m not shy about my interpretation being founded on that assumption. I think it’s a pretty good assumption. The alternative would be that the rule books contain some text that isn’t rules, and doesn’t call that text out as special. Now, maybe that is indeed the case, and if it is, my position doesn’t really hold up. But as the text is unclear on the matter, we have to assume one way or the other. Any interpretation of the text must be based either on the assumption that the text in question is rules, or the assumption that it is not. Personally, I think the assumption that the text in the rule book is rules is the stronger one.