Video player volume control

In edit mode, the video player shows a volume control/mute button:
The sign language videos I’m working on had some background noise and no useful sound, so I muted them. But I see that when I publish the book, the audio is not muted. And the next time I edit the book, the audio is no longer muted. Was the setting on that control supposed to persist from one editing session to the next and in the resulting publication?

Right, we don’t have any volume control settings for videos. The screenshot there appears to be volume on a player.