Why hadn't his Master said them? When he'd said that Yaddle's death was his fault, Obi-Wan had remained silent.
He knew in his bones that he had caused a chain of events that led to a Jedi Master's murder. Even if that didn't make him responsible, he knew it would make it hard for him to sleep at night.
The vision hadn't been wrong. The essential truth it had left him with was part of him now. He felt it inside him like a wound. It was loss. The gulf between him and Obi-Wan was wider than ever.