Maybe a randomized serial number will allow Apple to sell you a product made in America or Europe without you needing to know the difference. Maybe it also grants Apple greater liberties when negotiating with existing suppliers.
What was the story with Fountain (FC) and Fremont (F) anyway?
https://beetstech.com/blog/decode-meaning-behind-apple-seria...
https://9to5mac.com/2013/01/25/apple-lists-quanta-computer-i...