Currently, if you click the 'X' on the top right while watching a replay or live game, it will exit to the main screen. If you do not move your mouse and click again soon after (not immediately, but enough time passes for you to clearly see the main menu) it reloads you back into what you were watching. If you move your mouse, it acts as normal.

You can do this with replays and live games.

It should function as buttons follow: Click 'X' to leave replay/live spectate of game. Upon seeing the main menu, the top right power button should if clicked should prompt the user if they are sure they want to quit the game. (this is seen in the last half of the video when the mouse is moved.

This has been an issue for a very long time.

It can be seen here: https://www.youtube.com/watch?v=T3K1Wr6pUiw