Although, I'm not sure why it seems to be called twice. That is weird to me.

From what I can tell, didSet seems to be working now. Swift 5, iOS 18.2

The way I fixed this was by putting the scroll view at index 0 in the storyboard and then programmatically moving whatever other view you want at index 0 to index 0. view.sendSubviewToBack(<#T##view: UIView##UIView#>) (This can be done in ViewDidLoad or wherever.)