This is an interesting idea. Doesn't it assume the interviewer has never met anyone from your ex-company before or implies that you left "under a cloud."

When doing user interviews for my salary estimate startup [1] I ask people if they've taken / thought about a negotiation class. I've been surprised how many have thought about it and how few have gone through with it. I doubt that this would be a recommended strategy in a negotiation class, but like my users, I haven't taken such a class either.

[1] https://peerwyse.com