I think he’s right.
That does not mean that FB is a waste of time or the online learning doesn’t work, although both are true at times. It means the relationships formed online are different from those formed f2f.
A FB ‘friend’ is not automatically a real friend. Real friendship (as well as lasting teacher-student relationships) are formed, like he says, over time. I think it is possible to build real friendships online, but just like in real life, it takes time. I suspect that it takes considerably MORE online time than it would in RL.