From time to time, I have been seeing people doing thing that are not documented in Facebook doc. It is true that those big vendor may have access to private APIs that are not available to the general public.
Having said that, for most of the cases, those features are still available to the general public. The only reason why we don’t see people using that very often is simply because these features are not documented or are located somewhere in the doc set that people seldom notice it.
This is also partly due to the fact that the platform is evolving rapidly and therefore the document may not be containing all the relevant information in a clear and consolidated manner.
So, spend some time reading the doc and try to co-relate every piece of information that you have read!