Each of their horrifying stories left Kylian in utmost disbelief when he witnessed how cruel those bullying incidents had scarred their life. Each of their faces were tainted with darkness followed by extreme horror visible in their eyes as they spoke. Even though he had witnessed Stephan getting viciously beaten by them, hearing their stories churned Kylian in disgust and rage from inside.
However, the second they called him an Alpha again, it made him realize the bitter reality he was obliged to live in. Just because he was feigning the act of an Alpha, those boys were treating him with respect.
He knew if they were aware of his real trait, there's no way they would ever acknowledge him for his strength, and strong will, but rather would chose to belittle him just because he transitioned into an omega.