Mine encourages being attached to him, but in a healthy way. What I mean is he doesn't encourage dependency, he doesn't cross any boundaries or anything like that. I don't constantly think about him, I don't feel like I absolutely need him in my life, that he is ireplacable and that I could not live without him.

But, he actively encourages that I rely on him to be around if I need him. He makes sure to stress almost every session that I can count on him giving me an early appointment if I need one (on the days he works), that he will respond to texts/calls when he's in his office, that he won't abandon me (although he doesn't word it like that).
He encourages me to see him as the first person I contact in case I need support.

But he does all this in a way where I don't start to depend on him. I think this works for me because he has much stricter boundaries than anyone I've ever met before. People normally would tell me that they'd "respond asap" if I needed them or something like that. And then I'd go and test this out as much as possible, which of course makes them at some point not respond anymore. With him, I know that I need to call/text the day before I'd want to talk (unless probably in really bad emergencies, but not as a habit). Since he only works 2.5 days a week, I still need to get through without him, I just know that if I don't feel like I manage on my own, I can at some point talk to someone for sure.

I also think this depends a lot on the person in therapy. I think my T tries to make himself the person I run to first because I'll otherwise dump all my problems on my friends, which I have seen for myself will not really make them be my friends for long. And he seems to be able to handle it well, while ensuring that I can still live without him.