At that level, any kind of in-person visit is a sign of mutual good will. Traveling to see someone is an act of respect, and opening your doors to someone honors that person. Not every interaction is zero-sum.
Cook made no mention at all of meeting with the CEO of the fifteenth-largest social network.
He thanked Cook for "taking him around" the campus, that sounds like in person to me.
Seems to me the reason there's no picture is that the visit wasn't for us, it was for them.