@Svelandria She notes his attitude toward her changed. He definitely pulled back on the "tough love" route because he realized that wasn't winning him anything but animosity. He screwed up the romantic atmosphere with the dance, though. Almost had a thing going there. Combine that with apparently everyone else passing her despite having OP artifacts, and her inferiority complex hit full force and cemented the negative feelings she had towards him.
Though, he is also still flirting with women constantly, so maybe he is just an idiot.
EDIT: No, he definitely knows. Pretty obvious he was sending those notes, but his popularity with women backfired in the moment. It also seems like he wanted her to go for a more prestigious job; maybe hoping that she could earn a noble title. Oddly enough, this manga is going the route where the social issues related to nobility are there, but the people of importance don't care. For example, the dad is supportive of the idea of his son getting romantic with a commoner.