I don't think it's unethical for a T to tell their professional opinion about anything. If it is their professional opinion that you were abuse, they should, in fact, say so. If you don't have conscious memories of abuse and don't feel like trying to find out if that was the case, then the T should drop this topic and work on your presenting problem. If you don't have conscious memories but want to find out if something happen, then the T should suggests the methods of doing it and it is your choice to go ahead with any of those or not. The T, however, also has the right to refer you out if they believe that the solution to your current problem is to uncover the memories of possible past abuse but you are not willing to go in that direction. So, you have your choice in this situation and the T has theirs.