This is simply not true. I am a Google employee, and I conduct both actual software engineer interviews and what we call "lunch interviews" (in quotes because it's kind of a silly name). For the latter, my only communication with the hiring team is for scheduling. I find out where to meet the candidate, and where to take them after lunch. That's it. I don't even know how I would leave feedback for a lunch interview if I wanted to.

The only way in which the "lunch interview" is an interview is in the reverse direction: it's the candidate's chance to ask all kinds of informal or random questions about Google. Other than that, it's really just a chance to give their brain a break, because let's face it, interviewing is stressful and doing six interviews in one day is pretty exhausting. It wouldn't be much of a break if we were testing them while they ate.

I guess if a candidate did something egregiously bad while we ate lunch, like jump kicking me or something, I'd probably go out of my way to track somebody down and tell them. But other than that, lunch is just... lunch! :)

as i said, if someone comes across as a jerk to you he won't be taken. that's the test. hopefully most people aren't jerk during interviews, i mean, that's a really dumb thing to do ;-)