If I play with a friend that is already my friend, the add friend button shouldn't appear anymore

I noticed this when I played a 2v2 match and at the end I friended my teammate. We kept playing but at the end of every match the add friend button was still there. The add friend button shouldn't be visible anymore if the teammate is already a friend. Or at least change the icon with a tick instead of a + to acknowledge that the player is already friended.