User blog comment:Xilinoc/Ch. 569 (You've been hit by / You've been struck by / Senbonzakura~)/@comment-2211792-20140220205734/@comment-11051098-20140221211914

That is a good theory.

AFAIK, Byakuya never really "saw" her or showed much care during the time after he adopted her into the clan. The only close moment I know about is when he told Rukia the truth about Hisana and why he didn't try to stop the decision of execution. We only saw him smile once, as a teenager in the TBTP mini-arc, and AFAIK never showed any emotions or anything.

Considering this, I don't think it's strange at all if his words about how strong she's become, affected her so much that it possibly exceeded the fear induced in her by Äs.