I don't think it's actual "love", but rather transference. When you think about it, proper therapy with proper boundaries will mean that the client will not know much about the therapist at all.

How can you truly love someone who you spend an hour or two with, at most twice a week? Love comes from really spending time with someone, getting to know them flaws and all, and still loving them. You can't do that in an hour or two time window with someone that you are paying to see.