This also fails to take into account that ISBNs also contain the publisher ID in them. So identical copies of a book could have different ISBNs depending on which markets they are sold in.
LOCKSS is short for:
Lots of copies keeps stuff safe.
This is for digital material where perpetual usage rights have been granted, but the original source might not be available. It’s also used to make sure that journal content from countries that censor remains available.
This all is mainly for libraries and their online collections.