Social apps should be separate and not baked in IMO. Believe it or not, many loathe FB and their privacy policy- or constant trickery of changing it.
you correct, but i think IOS like android should allow you to sgare between apps, then reguardless if built-in or not you share whatever you like to and from whatever app.
So, in an Apple world restricting sharing between apps their only solution is to bake it in.