It likely doesn't account for the evolving definition of what a "close" friend actually is. Just because Jack and Jill know a bunch of details about each other

It likely doesn't account for the evolving definition of what a "close" friend actually is. Just because Jack and Jill know a bunch of details about each others' lives owing to facebook updates or group chats, that doesn't necessarily mean they share a strong connection, at least not in the traditional sense. But I suspect they might still feel a certain connection and belonging to each other. It used to require frequent, active, quality communication to know someone well. Now it just requires a few clicks.