For larger files, the malware generates four of these codes. But due to a programming error, it keeps overwriting each new code with the previous one in the same slot, like writing four different combinations on a single sticky note and keeping only the last one. By the time it’s done, three of the four codes are gone forever. The scrambled data they correspond to is permanently unreadable for the victim, security researchers, and the attackers themselves.
Overwritten is fine when that is intentional. But the best backups do include media that is completely offline and so if there is an issue you can restore to fresh/new uncompromised systems.
ZFS snapshots are great for this - so far they have not been attacked and when they work they give you what the file was before. (you still should have an offline copy of everything stored in a different campus)