Often it is connected with infringement of file structure of internal memory or a SD - card. (e-ink-reader.ru)
An ebook and PDF version of your manuscript are both your book, yet their unique file structures mean they serve different functions. (millcitypress.net)
But you're absolutely right that there are best practices for things like file structures and naming conventions, but there aren't rules or paperless police that you have to adhere to. (lawyerist.com)