It could depend on what the therapist (correctly or not) thinks about the client. The ones I have seen have all over-acted excessive enthusiasm whenever they thought I was reaching out to them. "Hurrah we got the avoidant dismissive person to bond with us" sort of thing. They were wrong, but the idea of it seemed to make them feel all smug and self-satisfied.
Perhaps they under-act or discourage those they think are too attaching and over act encouraging those they believe to be not attaching. I think they are arrogant enough to believe they know such a thing and then try to manipulate clients around it. I find them an arrogant lot to begin with. I completely believe they have a therapist persona. I have a professor persona and a lawyer persona. It may have bits of my true personality in there - but I do not treat/talk to/think about etc my students and clients like I do my friends and loved ones. It does not bother me - I paid the therapist to act a role. I believe that is what they do.