Expected Behavior: I expected that when the browser window was dragged from being in maximized mode to windowed mode that is less than the "xl" size that the fixed side nav would hide and the button with the "hamburger" icon would appear on the navbar to toggle the side nav.

Actual Behavior: When the browser window is dragged from maximized mode to windowed mode that is less than the "xl" size, the side nav does not hide, but the navbar animates as if it expects the sidenav to hide. However, when I resize the browser window by dragging the edges, the sidenav hides. Finally, after toggling the sidenav via the "hamburger" button, the sidenav shows and hides as expected as the window is taken into and out of maximized mode.

Resources: The best example is actually the MDB website itself. I have uploaded a gif to Imgur showing this issue.