Many other parts of the world value honor and honesty more. I'm from one of those parts. In this case, it's a prisoner's dilemma. Honesty doesn't benefit you, but if everyone's honest, it benefits everyone. Exit interview, it doesn't hurt too much either. It's a safe time to be honest.
Having been on the other side of the table, if your manager is professional -- and most managers are -- it's a numbers game. The odds of an exit interview having an impact are close to zero. It's one person's issue. That doesn't make it invalid -- if you have a 30 minute longer commute to the new office, hate the way we do performance evaluations, or want growth paths into product management, you've got a valid reason to leave.
If five people hate the new location, how we do performance reviews, or don't think they have good internal growth paths, I'll act on that.