Completely unintentional my ass...
Yyyeah, they just so happen to put in a secret thing with Korean text on it right after Half Life 2's sudden change to Korean
It does seem like that they were just trying to rake in some attention for their ARG
I guess it makes sense since they wanted to do an ARG but wasn't sure if their fanbase was big enough or smart enough to figure it out, so they wanted some of Valve's fanbase because they've been able to thoroughly investigate whatever ARG they cook up