I had a far more honest rejection, because I knew the manager. "Our system indicates that you could get a better job than us, and we don't want to waste all that money training you only to leave when a better offer comes along. We want college humanities majors who are so happy to be working with books, they don't question their hours or how much we pay them. Or someone that thinks this is the best they could possibly do for themselves, which we call "commitment to being a career employee" to HR."
I asked which she was - perhaps not the most diplomatic answer, but she HAD just refused to hire me.
She smiled sadly. "I have three kids under 10. This *is* the best I can do."
She was also an English Literature major.
So, rather than dismissing your accomplishments, maybe they're suggesting that they know you're better than them.