The foot work is just very subtle, they is lots of movement but it's tiny movements.
The hopping/foot tapping is a tool, it's not a stance. A few guys fight with the weight fully on the rear foot, front foot tapping all the time but not many. Most guy rock their weight, front foot, back foot, front foot, back foot, not 100% standing on one leg, but maybe 70:30. That's the reason they look like they're dancing, they are shifting their weight. As they shift their weight, they shuffle.
As you shift your weight back it frees up your lead check, switch kick, lead knee, jab, as you move. As you shift your weight forward, your rear kick, rear knee, rear cross are all free.
The foot tapping is part of the game to land your own strikes. If you start to load up your front leg or start moving to your left, I might shift my weight back and start tapping my lead leg to show you "if you kick I'm checking that!" You could be just out of range and I tap to warn you off bull rushing in unless you want a teep. I can load up the lead leg and threaten a right kick, you check, I punch instead.
Subtle stuff. Easiest way to start is think, weight to the rear I can attack/defend with lead weapons, weight at the front means rear weapons.