Additional meeting and call-related features and issues within Microsoft Teams for business
Microsoft has obviously not done any User-centred testing on this issue. I studied usability and it's beyond belief that you can't determine where each field of the screen is positioned.
To have the video streams at the bottom is absolutely ridiculous (as everyone else has said). It needs to be at the top so that you are appearing to have eye contact with other participants.
PLEASE FIX THIS MICROSOFT!