Why Would A Therapists Reflect When Clients Hold Back Their True Feelings?

As an autistic person, I often have to consciously think about what is considered socially acceptable to say in conversations. In therapy, I recently realized that at the start of discussing a topic, I was avoiding saying certain things because I felt they might not be appropriate. I later shared this with my therapist, and she expressed sadness that I didn’t feel comfortable enough to say those things right away, emphasizing that therapy is a safe space. She mentioned she would reflect on this and make an effort to ask if what I’m saying is how I ‘really’ feel. I’m wondering—did I do something wrong by filtering my thoughts initially? Why might my therapist feel responsible for me feeling guarded in therapy?