I think the point of this article is the difference between standing next to someone and online conversations. While I agree that is a major hint, especially in certain cases (especially in the sense of the stalker-esque men hounding women through DMs on social media), I've had very long periods of non-communication with long-distance friends I still consider "close" that pick up much later, sometimes with multiple messages on either side with varying degrees of response.
It just depends on the nature of the message. If one side is just amassing a list of things or a complete idea to digest on the recepient's own time, with the mutual understanding that people lead busy lives, it's a bit different than say, someone repeatedly ignoring a particular request or general attempts to start a live conversation.
