I don't see it necessary to "empty out muscle glycogen" as that could be dangerous. I do think the goal is to empty out liver glycogen but this happens on it's own. HIIT does tax the muscle glycogen stores but I think it will result in bonking if you deliberately do it and then fast on top of it.

It takes carbs to do HIIT in the first place. You can do it while in ketosis but it is less studied.