Earlier quoted context omitted.
I've read that being rejected at a committee level happens relatively infrequent. Did they hint to what might be the reason for rejection at such a late stage?
It happens all the time. The first couple of interviews are just a phone screen. After the on-sites the packet goes to a committee, always, which makes the final decision having read all the feedbacks from all the interviews. The hiring committee isn't some last moment check/balance, it's the primary way hiring decisions are made. Or at least that's how it worked when I was an interviewer at Google.
From what I understand, reruiters are rated based on the quality of candidates they pass to the hiring committee, so they have an incentive to only let the best pass.