I don't even have a linkedin work persona. its an online resume as well as a way to stay in touch with coworkers mainly by getting or giving recommendations. I don't get why anyone posts there.
Dude was probably being set up for an arranged marriage by his family, which can potentially pair you with someone you do not share any interests with or even attracted to in the first place. With that context, it kinda makes sense that he wants someone who at least shares something similar with him, and I guess linkedin is one way of finding out (in his mind).
On the one hand, the idea of using linkedin as a dating website is irredeemably terrible. On the other hand, if singles who think otherwise actually follow through with it, that saves a bit of time and frustration for a lot of other people.
Premium subscription that allows messaging people out of your network and provides a bunch of analytics about profile/article views. I know sales, marketing, and recruiting people that love it.