my experience is that this actually does limit cheating, but it doesn't prevent it.
the sale of KSSNs, kids taking their parents to get more accounts to get banned, keylogged KSSN/accounts/compromised mobile phones with malware being used to receive verification sms (originating from downloading pirated games and pressing yes) is commonplace
there are numerous chinese sites where you can go buy a korean ssn-verified account for $1 or less, cheaper in bulk. they are rarely used for making a "main" because you are subject to lose them at any time to reverification, so they're largely used for throwaway activities.
the sale of KSSNs, kids taking their parents to get more accounts to get banned, keylogged KSSN/accounts/compromised mobile phones with malware being used to receive verification sms (originating from downloading pirated games and pressing yes) is commonplace
there are numerous chinese sites where you can go buy a korean ssn-verified account for $1 or less, cheaper in bulk. they are rarely used for making a "main" because you are subject to lose them at any time to reverification, so they're largely used for throwaway activities.