The book is a role-playing game, and such PDFs are usually presented in single pages, not in spreads. So, I could do everything in spreads, but it would stand out among other such products, which isn’t a good thing, I think.
There are only two spreads in the entire book which contain a single picture, one of them being a map of a large area. So I thought keeping these two spreads as spreads while everything else is a single page would be a better solution.