Probably registers as a positive usage metric for the app bar.
Bingo. Engagement = Good! (even if the engagement is accidental or out of frustration) The line goes up!
Or you can make it go away completely with: https://zoom.us/profile/setting and search for 'apps'. Turn off "Zoom Apps Quick Launch Button" and I believe that makes the dock go away, too.
Not permanently. I’m finding that I have to close it on ‘every’ call.
It has an option to "auto open", which you can deselect.