Consider StarCraft: Brood War, a legendary real-time strategy game. To be played well, it requires between 200-400 actions per minute (APM), with some players going even beyond 500 APM. Some games last for more than an hour. Players use both the mouse and the keyboard. There's always more to do than you can realistically do. You are always putting out fires, managing your economy, producing units, securing income, carrying multiple attacks at once, fighting tactical battles, and executing strategic goals. Yeah I'd call that a pretty active sitting :)
Let's be honest, most of those actions are useless keybashing and clicking. It's easy to get a high APM.
This is certainly true in the beginning of a game. Players claim to do this to warm up. However, in a busy confrontation there is no reason to spam any actions that are not directly contributing towards your endeavor. If you spam useless actions during a fight, your opponent who does not will best you.
In Smash? Sure. In StarCraft? I’ve never measured it, but I wouldn’t say ‘most’ by any stretch.
The game's been played competitively for more than 25 years now, people still earn their living plying StarCraft. You wont find a single one of them with APM below 200. Having their livelihoods and legacies depending on this, do you think they'd be repeatedly doing something useless instead of optimizing?
Anyways, I think you are missing the point that this thread is about active sitting. I imagine there isn't much difference to the meaning behind movement: movement is movement, meaningful or not.