Why does Apple deny an accidental App purchase by a minor?

My 6 year old daughter made an accidental/unauthorized in-App purchase ("Banquet Pack" $54.99). I immediately deleted the app and requested refund for the purchase. Apple denied by request twice. So I contacted the support via chat. She/he said she/he could not disclose the reason for the denied refund due to security reasons. Then she/he just referred me to their terms and conditions page, pointed to their refund policy, where it says "From time to time, Apple may refuse a refund request if we find evidence of fraud, refund abuse, or other manipulative behavior that entitles Apple to a corresponding counterclaim." So I asked, which of the "evidence of fraud", "refund abuse", or "other manipulative behavior" applied to my case?. She/he couldn't answer that question either. Then he/she just gave me a general service support number. how could this cause a security concern? why do they not refund me or at least tell me why?