Apple is doing its job.

There is no way for it to accurately determine the legitimate owner.

So better to err on the side of caution and assume that if you're coming to Apple with an unlock request that it's not legitimate.

They can tie your purchase to a serial number. It’s listed on the invoice. That should constitute proof in my opinion.

Apple hasn’t yet figured out how to stop people from selling their used equipment.

Many Apple products are bought from third party resellers who don't capture this information.

That's not relevant to the case at hand, where OP was actually able to prove that he'd originally bought the device.

And the owner could have sold it and stolen it back in in the many months he have bought it. I guess if you manage to block the device in the store itself, they will unblock it for you - but it would defeat the purpose in this case.

They have to work on the balance of probabilities though. It would be very long odds to sell a device, steal it back, then need to approach Apple for help unlocking.

They can't rely on the odds, because scammers would step in and increase the odds if the possibility existed to exploit Apple's behavior. IMO, this is what should happen given that Activation Lock is enabled.

It's a separate question whether the customer should be able to disable Activation Lock before it gets tripped, which would prevent the computer from bricking itself. Apple makes that choice for the customer because they don't fully respect your ownership of the device that they made.

This is the dumbest argument.

They know who bought it and that person can proof their identity.

And they don’t know whether they might have sold it for someone else.

A police report made before or right around when the activation lock was implemented could be a pretty good indication on whether or not it's been stolen.