I think there's a problem in assuming that all therapists use the relationship as part of therapy. That type of therapist (who doesn't use the relationship in that way) can be easily wounded thinking that their professional skill is being criticized if a problem is brought to their attention, and a wounded therapist can be dangerous for someone in a vulnerable state.

For those therapists who do use the therapy relationship, talking about ruptures is clearly helpful.

The problem is in not knowing how a therapist operates until things get heated, so there's a lot of risk taking on the part of the person that can end badly. This is not to say that those who don't address ruptures are bad therapists--it's just that they don't follow that model, and it's a problem for the person who doesn't know how to proceed and doesn't want to risk making things worse.