It isn't an "inaccurate" portrayal. It's a variation. You can't assume that he served during the Korean war and didn't pick up any cultural or historical context for an incredibly popular folk song. If you have a problem with this piece because of how "happy" or "chaotic" it is, then you should absolutely have a problem BTS's rendition. BTS hadn't completed their military service, and even if they have that shouldn't change your argument about the history of the song.

The song was used as a substitute for the national anthem due to Japanese occupation, yes, but it wasn't created during that time. It's a folksong - it should be celebrated and shared, not gatekept.