Until the EPUB working group demands that all devices
must support and pass a standard certification to a minimum required feature list, you have what you have now:
A PITA for book developers

16+ different renderings because various manufacturers chose to interpret (or ignore) the EPUB
guidelines.
The EPUB file extension and Logo need to have a License (Low or No cost) before they be used on a book. The License specifies that minimum compliance has been met for this article. (USB has such a policy, unfortunately it appears to have a hefty FEE)