The guy whining in the blog post exactly opted in.
He clearly did not give his full consent because the UI was designed to bury the thing that he would have explicitly opted-out of.
> FounderDating asked me to identify ten that I would vouch for. I didn’t have to do it but I thought oh well, I guess I’ll do it and see what happens. So all I did was click their photos. Nothing more.
Can't speak to the rest of the flow but clicking photos indeed sounds like opting in.
I can see how it'd be easy to miss the fact that this will send an email, although it's stated unambiguously, at the top of the page, and underlined. And it's definitely opt-in. I have to select folks.