I think you may be misunderstanding the purpose of e-book formats like epub. It’s not like PDF or word documents, where the file dictates the exact layout of each page, or even how many pages are in a book.

Rather it’s meant to be a flexible description of a book, that adapts to different screen sizes. More like old websites than a book. So, with a larger screen, more words may fit on a page, so there’s fewer pages. This also means the exact location of an image isn’t fixed.

This is not a bug or bad rendering, it’s working as designed. The reader/user usually decides the font, font size, margins, line spacing etc.

If a book requires precise positioning, control over pages etx., epub is the wrong format, you need pdf