"Is there a reason to force downgrade system audio output streaming on specific device?"
Indeed, there is. You are encouraged to use Teams on Windows, preferably. It has a vastly improved user experience, including removal of Full Screen view.
In the Windows version of Teams, it is no more possible to use the entire screen for displaying shared content. The meeting controls remain fixed on the top right of the Teams window. All the "Full Screen" feature does is removing the window decoration from the Teams window.
This is currently celebrated by Teams enthusiasts all over the world as the greatest improvement in Teams usability ever, and makes Teams superior to all other videoconferencing platforms.
For technical reasons, this brilliant feature is currently available for the Windows version only, and that's why everybody is strongly encouraged by Microsoft to use this version.