Those refunds are for purchased hardware. As long as the item is undamaged, you can bring back any Mac, iPhone, etc. within 14 days of purchase for a full refund, no questions asked.
The 14 day window does not apply to the App Store (for nearly all items) as your purchase is not from Apple, but the third party vendor who created the app.
I assume you already tried this?
Request a refund for apps or content that you bought from Apple - Apple Support
If so, then you have no other recourse. It's up to the owner of the device to set it up so a passcode is required to make purchases.
On a newer iPhone (I'm looking at iOS 17.x)
Settings > your name at the top > Media & Purchases > Password Settings > Always Require Password