If there is transparency for any elements transformed in 3d space it is essential that a sorting algorithm be specified, otherwise, webpages will get vastly different results depending on the sorting algorithm, or lack of sorting algorithm used.

A simple "coverflow" style page where all the images are at the same z distance from the camera, all are overlapping and all have some percentage of transparency will not work display the way a designer expects them to display without sorting.

Different sorting algorithms will end up with different result requiring designers to go to extreme measures for each and every different implementation.