Utter nonsense.
There are plenty of kids who can’t serve even if they wanted to. The circumstances are not of their choosing. I.e. they did not acquire foreign citizenship on their own will and they did not choose to live overseas. The Korean law clearly recognizes this special case and allows them to lawfully give up the citizenship if certain conditions are met. The conditions exist to exclude those who did “won-jeong-chul-san”. It is a lawful process and they are stripped of any rights as a Korean or a former Korean. It is as simple as that. They are simply treated as foreigners without any special (negative or positive) treatment.