When the flag is zero, it will set ret=0 instead of ret={error} when verifying a RSA signature fails. This RSA signature seems to be the signature in the [[NPDM]] ACID. It then skips verifying what seems to be the second signature in the [[NCA_Format|NCA header]]. Note that if verifying the NPDM(?) signature is successful, and verifying that second signature fails, it will throw an error and abort.