If you start searching for an “unrated” VERSUS game immediately after starting the game, the search occurs for RATED lobbies, and not “unrated”.
I end up losing my rating every time because I thought I was playing in an unrated lobby! I usually go to “Unrated” to experiment with tactics or for fun, but every time at the end of the battle it turned out that it was a game for rating!!! 
Moreover, in the lobby itself there are no notes anywhere that I am playing in the rating! In addition, it is extremely strange that there is no “confirm game start” button when searching for a rated game - the game starts instantly and this is very bad…
The error has been around for a long time, why hasn’t it been fixed yet???
We never needed a “confirm game start”… you’re supposed know what game you’re playing when you play it, and you can always cancel the queue. The game does not start instantly, it starts when it finds an opponent.
That said, I was able to reproduce this after trying just now. It seems to be a bug with the menu UI- it saves your previous selection when you quit the game, so if you closed the game with Unranked selected, it will show that when you next open the game but it still actually defaults to ranked.
There seems to be a workaround for this by selecting Ranked from the buttons at the top and then going back to unranked. You can also make sure the game is in ranked before you quit, so that you must select unranked to play it.