Doctors did not permit their patients to suffer poorly-set broken arms. This injury, Leto feared, was deeper by far - but the principle was sound. A weaker person would have shied away from causing pain to someone they cared about, even if that pain was needed. Leto was unafraid of the difficult choices.
"Why would I know what they look like?" he asked as softly as before. It was clear what she wanted, what she'd always wanted. But to give it to her would be to continue to lie to her. And now, now, she had a reason to try.
She didn't know it yet, but she had a very good reason.