I think it depends on what you mean by blank slate. If you mean absolutely no sharing of thoughts or opinions on what you're talking about it therapy, that's different than not sharing personal information and experiences. I think the latter is lot easier to deal with than the former.

My T does not share anything about his life, beyond what's revealed by the diplomas on the wall and decor in his office. But he routinely shares his thoughts and opinions on what I talk about. I know where he stands on almost everything I bring up. I feel very tightly connected to him, even though I have no idea whether he has kids or if his parents are still alive or what tv shows he's seen.