My T has self disclosed but only because she believed I wanted her to and that be helpful. It was mostly basic stuff, but I don't find that I really want to know. It came up because I was explain how she's a stranger, and how it was difficult to remember she was a person too and that existed outside of therapy.
It helped a little to round her out as person in my mind. I haven't asked much, and she doesn't say much. I wouldn't want a therapist that self disclosed a lot. I can remember my first therapist doing it a lot, and in my mind going "I don't care" "did I ask?" "why are you telling me this"