But what has Fleabag actually revealed about herself to the priest? We know her secrets, but he still doesn't, I don't think?
She told him about wanting to be told what to do, and about having had a lot of sex. He already told her pretty much exactly the same things about himself in episode three, so they're equal there. Priest doesn't know anything at all about the existence or death of Boo, about how FB's mother died, why she runs the cafe, why she fell out with Claire, anything. All he actually knows is that FB doesn't appear to get along with her family, that she's sad and has had a lot of sex, and is an atheist. And that she didn't have a miscarriage. He's not psychic.
In the confession booth, he asked her to tell him her secrets "because it'll make you feel better, and because I want to know". That's pretty open, not manipulative. And she didn't actually tell him all her secrets. She was more honest with the therapist than she has been with the priest.
Meanwhile, she actually knows a lot about his personal life - his parents were alcoholics, his mother a lesbian, his brother a paedophile, he was having a lot of meaningless sex before finding the priesthood and now he feels he has found peace with God, though he doubts it every day and drinks heavily. That's quite a lot really.