I've got a bit of an issue here, but I didn't notice it until I took a closer look at the tub flange. When the wall was framed, it was plumb and square to the back wall of the house. As the lumber has dried over the past couple weeks, it went all wonky and caused the wall to come out of plumb in two directions. I had to pull all of this down and shim all the studs to get the wall flat and true again.

Not doing so would have meant the tub would look crooked against the wall and the tile would not have been able to "fly" past the flange. Not a hard fix, but something that wouldn't happen if you could get actual kiln-dried lumber.