I agree with this. I only use m4v for one purpose, audiobooks. The Plex app on Roku will play a video file with no video part and allow full control like FF, RW and resume while audio files are problematic, at best.
I simply rename my audio books from mp3 to m4v and voila a fully functional audiobook. Note: This only works on Roku and in the web interface and Emby does not support this trick. I use m4v so I can easily tell when I am in an audio folder as I use mp4 for “real” videos.
Although I did not say earlier I actually use sXXeYY with lowercase “s” and “e” It is not really “better” at all but for me it is easier to read and it somehow seems to fit better with the way I see file names.