[kjaftaedi]

All humans sweat, also that smell could be from not washing his clothes properly.

Underarm BO is a totally separate thing, and he's right that most all koreans and east asians don't need to worry about the bacteria that causes that particular smell.

If you go to korea, you'd have a hard time even finding a place that sells deodorant.

So your old coworker is either in a very small minority group, or just had other hygiene problems that are not specifically underarm BO.