EPUB books don't maintain stats.
The issue is confusing, as I sideload EPUB's as wel, but I've got the KoboTouchExtended driver configured in such a way that it will convert the books to KEPUB on the fly. So, you can indeed sideload EPUB's, and then end up with KEPUB on the reader without noticing, thinking you're reading EPUB's but actually, you're not
