Usually yeah, but South Korea has a really high rate of circumcision. I think, as in many other countries, this could be changing *as of now*, but whenever Wonho was born, it was probably common practice yeah.
What's pretty crazy though is that I believe that for the most part it's done when boys are older (a little bit before teenage years-ish?) as opposed to when they are freshly born. I feel like since it's done that way, there's always a bit of a bigger "unknown variable" because what if the young dude is incredibly scared shitless he doesn't want to do it? If the mother is somehow against it, thinks it's unnecessary? etc.