It’s my understanding that mass produced items are all basically the same. If you buy something like a toothbrush, for example, then any other toothbrush from that same assembly line is going to be basically the same and have all the same specs (with the exception with minor defects here and there), because the machinery and process to make any those toothbrushes are all basically the same.
But that can’t be the case with locks and keys. Because if every lock and key were the same then there’d be no point in having them. Anyone could just bought the same key/lock combo could use it to unlock your front door. So all or most keys and locks must be unique. So how are they mass produced in a way that preserves their uniqueness?
Your confusion stems from the bureaucracy, not the method. Even if it was ‘simple as’, the result is the same.
Some doors yes, other doors you have to take the whole thing apart. I would say most are not ‘easy’. I don’t know the outcome, I think they were rekeyed because I was told to keep the lock even if I replaced it. I left that week for unrelated reasons and had my property manager deal with it.