Those not up to snuff were snuffed out like their parents. At some point the subjects of the tests learned what was happening and rebelled, killing the scientists and escaping. Wherever those kids wound up, it's gotta be a better place than Vault 75. Now it's inhabited by Gunners, ...
Inside the safe are the snuff tapes. With the evidence, the player character can go back to Cachino, who will give them the option to confront Clanden with the tapes, or they can just confront Clanden themselves. Telling Clanden that they have the tapes gives them the option of ...