This is fascinating to me. Surely Apple has a databases somewhere of all the S/Ns of all the computers they've ever sold. Why would they accept a made up one and insert it into their database?
I've long wondered that too! I have to assume that, for some kind of manufacturing reason, Apple either doesn't have such a database or doesn't trust its accuracy.
If anyone with more knowledge of supply chain dynamics knows why this might be, please feel free to chime to chime in!