I'm also fully unqualified, but short of the person that authentified the device coming up and detailing how they're the current owner, I still think a person with physical and proof of purchase should be prioritized.
If for instance the device had been sold to a different owner, that owner should have the receipt and be contactable (they have the email address and probably other info). And if the owner declared theft, we're out of Apple's field and it should be an official claim.
I see the passing down to a family member situation in the same light: if it was an informal transaction, the official owner is a still the same, and getting back the device unbricked and wiped out shouldn't be an ethical connundrum.
The thing that gives me the most pause is that Apple keeping a hard line on refusing to unbrick the device means they get an additional purchase from someone who's already heavily invested in the ecosystem. From their POV, bricking more devices has no counter incentives.