Eh, it's more likely that the statistics that come out of North Korea are so few and so unreliable that there's no reason to specify that they're talking about South Korea, it's just assumed by most that they aren't talking about the Hermit Kingdom.

And fwiw the South Koreans refer to their own country as 대한민국 daehanmiguk - the Great Korean People's Country and the North call themselves 조선 Joseon (or more specifically the Democratic People's Republic of Joseon), the name of the last Korean dynasty. Neither refer to each other as "North" or "South" and they discourage the use of divided names because it implies the goal of both isn't unification.