I suppose the awkward part of blacklisting is that if a phone isn't immediately reported, someone may sell a stolen part to a repair business, which installs it, and then a week later the customers phone is locked down, through no fault of either the person who had their phone repaired or the repair shop
A repair business doing that wouldn't be in business for long though.
There are APIs available for verifying whether FindMy is disabled for the device in question, that might be a better proof that the device is honestly sold to a repair shop for parts.
For devices broken enough that they don't turn on there needs to be a way to remove them from FindMy without using the device though... is removing them from the list available at https://appleid.apple.com enough?
That's a situation where some kind of delay could handle it. They don't need to reuse those parts instantly. I doubt the fraction of people that report a theft after months have gone by is very big.
The customer then kicks up a fuss, the repairman realises that the part came from a stolen phone and the supplier of these parts is either reported or blacklisted by the repairman and every other repairman they know.
