I have exclusively used the app to play "friendly" games with family/friends. We don't care about rankings. It would be great to have a "Take back move" option (With consent of other player) for scenarios where you make an obvious mistake and you both want a fun game rather than to mercilessly crush every mistake for ranking points!
I think if it's used right than it's a good option. For instance if white goes to castle and puts his king on f1 by mistake and asks for a redo, there's nothing wrong with that. But a lot of players would be hitting that button for everything they miss, every blunder, and I think that's why it's better that there isn't one.