Facebook SDK is one of the worst SDK I have implemented. They constantly changing their APIs on each version, and its driving me nuts as developer.
When you are using iOS9 with SDK 4.6+, you are no longer get fast-app switching. It will open the Safari instead. The bad thing with this behaviour is, user will need to enter his username and password again. This is one other reason not to use Facebook SDK anymore in my next project. Unless the client asked it.
I am not sure why we should put few of their URL Schemes on our plist file if they couldn’t use the fast-app switching. You may need to read this in detail on this Stackoverflow post.
Bye-bye Facebook SDK!