A-to-z Guarantee Claim - What is the point of delivery confirmation?

Customer buys book. I post book by Tracked delivery. Customer says tracking shows delivery but book stolen. Customer opens a claim ( 3 weeks later), Amazon refund customer. I appeal. Stating tracking, picture & GPS shows delivery. Amazon says 'computer says no'.

What is the point in sending items tracked/signed if Amazon dont believe delivery confirmations?

Principles mean nothing any more. Rant over.