This just came up today because it looks like Apple activated the short links betweens apps.
When creating a SLComposeViewController using SLServiceTypeFacebook and presenting it, right now a new bar appears at the bottom with two options "Write Post" & "Search". If you tap outside the bar the callback is called with the result SLComposeViewControllerResultDone instead of SLComposeViewControllerResultCancelled.
This seems like a new feature and looks like a bug from Apple. I did fill a bug, mainly just raising attention so more people see it