Wouldn't admitting this in court pin you with some sort of negligence? (if you knew having a schema revealed would compromise your app in some way).
Edit: More NULL, or maybe lack thereof cause they use the string "NULL" instead? https://news.ycombinator.com/item?id=20676904
It wouldn't. I'm just assuming that the thrust of the hypothetical negligence accusation was "The schema is useless unless you have SQL injection holes. So give us the schema or admit you are negligent!" But you're correct that there are other justifications one could make to keep the schema secret.