This discrepancy has been fixed. Now, both text fields consistently state Kungcho Island.
As a sidenote, the Korean name for the zone on the Northern Continent is "동부섬". It's my understanding that "동부" means "eastern" or "east side", while "섬" means "island."
I would assume that East Island was the correct localization of "동부섬", not Kungcho Island. This is also supported by other in-game texts, like how achievements state "Defeat the East Island Bounty Target 1 time".
This of course isn't a big deal, and I think most people neither care or notice. But I would appreciate if these text errors are sufficiently revised before implemented.