It is automated and I have seen no mention of being able to prevent it. I could see Apple deeming it should be done in this context:
Family purchases and payments - https://support.apple.com/HT201079
"If you're the family organizer and you don't recognize a charge
Search your email for a receipt. Apple emails a receipt to you when your family members buy items and when their subscriptions renew. The receipt shows the Apple ID of the family member who made the purchase. If you still don't recognize the charge, learn how to identify an unfamiliar charge [ https://support.apple.com/HT201382 ]."