Or when the mouse starts entering the target before the click at least?
It could. That’s the point
Control center is responsible for drawing a bunch of the ui on the top right of the menu bar, things like the clock (many comments here seem to be saying this is related to showing seconds), Wi-Fi, sound settings, etc.
It also shows the annoying overlay bit when you accidentally open it :D
Indeed! When "Display the time with seconds" is enabled for the menu bar clock, Control Center sits at 0.8% CPU activity instead of 0.0% on my Mac.
I think part of the confusion is that there's the feature "Control Center" and the process controlcenter so you would reasonably think it's only involved in the marketing feature's UI.