At present, the package is careful to number only the recto pages since, in the way the package is currently conceived, they're the only ones with 'content', and the verso pages are notes. However this is not the only application, and it would be reasonable to have these pages numbered as well.
Given that those pages are included in the numbering sequence, there's a separate question about whether the numbers should appear on the page.
(from a suggestion by Axel Berger)
On investigation, this has turned out to be somewhat more intricate than I expected, especially in parallel with the recto changes of issue #1.
While this functionality would be nice, I suppose, it's not obvious to me that it's worth the maintenance effort, and so I'm tempted to downgrade its priority.