I think this is a matter of semantics; I'm not sure if they're actually feeling "love", or just a personal connection. Not surprising that a bunch of clinical researchers would be unclear on the distinction.
I've been in full-on love twice. Both times, I felt a connection with the guy almost immediately after spending time together in close proximity. But I didn't feel actual love until I knew him inside and out. Finding things to like about someone is easy, but in each case I knew it was love when I truly understood and accepted all his flaws.
Having said that, it's a very interesting study and I'd definitely like to participate! Any volunteers?