I thought of both of these things -- but look at the places he interviewed. They spent a lot of time with him (sometimes several days!) and he was largely dealing with technical folk, not HR people.

I'll bet if he asked them all in the right tone -- and without demanding a lot of time -- he'd get at least a few responses.

I know it's possible, because I've read several posts in the past from people both saying they've done this (and providing some details), plus others on the hiring side saying they'll generally give useful feedback if asked at the end of the interview process.