I get your point. I think it would bother me that's it's a robot/machine vs a real human, but that's just me. The same way that venting to my pet is somewhat cathartic but not very much compared to doing the same at my SO/parents/friends.
I don't disagree with you. It feels somehow wrong to engage in theory of mind and the concomitant effects on your personality with an AI owned by a corporation. If OpenAI wished to, they could use it for insidious manipulation.