Delivery confirmation no longer a valid defense against Amazon A-Z claim?

Today Amazon granted an A-Z claim for an item which had delivery confirmation. In fact, the customer admitted (via email) that the item arrived *after* she filed the claim, but didn't know how to withdraw her A-Z.

Amazon subtracted the money from our account, and sent us this message:

"Thank you for your response. Unfortunately the tracking information you provided does not include signature confirmation of delivery. As a result, this is insufficient evidence of delivery to the intended recipient. Note that many carriers, including the USPS, use a delivery confirmation that does not confirm delivery to the recipient's address, but instead only confirm delivery to the zip code."

So now *signature confirmation* is necessary for every order, or less sellers are not covered by the A-Z guarantee? Makes no sense, because the A-Z program is insurance that ever seller buys into! (that's what the $1.35 variable closing fee allegedly pays for).

Fortunately, this does not affect FBA sellers. FBA sellers have NO A-Z coverage. They continue to be charged the $1.35 variable closing fee, but receive no benefits.