"Actually that post was just an attraction with nothing substantial behind it; they had not spent time together other than flirting at work."
Exactly the point; people constantly are disappointed in "love" because they don't see the desired one for what they really are, but what they WANT the beloved to be -it's called "projection". Beginning dating is pretty much the same while the parties reconcile their expectations with the reality!
Spending a few minutes or hours in someone's arms in the car does not a relationship make, so I think it wise to play it cool until the doubts diminish. So far it seems pretty much in the infatuation stage, as the most intimacy he's shared is she "can hang out" if he ever gets his own place.