Lucifer is used to that response. Without other input his natural politeness put people in the mind of celestial angels which did not have children. They followed the edicts of God. Lucifer did not.

"Yes, my son. He was blinded...." Lucifer pauses wondering what to say. By Michael is lingering and about to be said but instead he changes directions with the comments, wings shifting in the moment of indecision. "... when he was the equivalent of a human teenager."

That was probably more meaningful to the human than anything about the war with heaven anyway. He's aware of the shift in his own energy. It comes across as a slight tension in his body and the physiological hints of anger that isn't being shown outright but buried. It takes a conscious action to subdue his own emotions and move the conversation to less tense territory. "He has a twin sister, too."