This changes the perception drastically and, more importantly, isn't a fair comparison. The "control" wasn't presented as 4 different messages and it makes total sense that sending more messages would appear more desperate.
Consider other mediums:
* Phone: someone leaving 4 voicemails in a row is perceived as super desperate in comparison to someone who leaves a single voicemail of the same total length. This is literally a sitcom trope.
* Email: someone sending 4 different emails (1 per paragraph) would definitely create a different (negative) impression than someone sending a single email
The author pretends to be demonstrating a way that the Facebook UI twists a message but is actually just affirming what is likely a universal trait of messaging: sending more messages before a response signals social awkwardness and desperation.