This is not about Koreans not feeling proud of the achievement but instead about Koreans actually streaming and supporting the song/album after knowing news. I’m not korean neither live in Korea but this is base on chart performance of the song/ album on digital platforms after the news.
Koreans don’t really care about Billboard achievements unless is something so big or never being done that is literally impossible to hide from the media so obviously Koreans end up watching it in the news and it gets insane buzz.
There is a misconception among kpop fans that expect Koreans to end up streaming and supporting the song/album after charting well on Billboard charts but that doesn’t happen specially with boygroups, for example: SuperM, Monsta x, NCT 127 and TXT groups that got top 10 and even 1 debuts didn’t get any extra or special support at all.
Top 10 debut on billboard 200, which isn’t an easy feature at all, barely gets attention because now a decent amount of groups get it. Currently many 4th generation group stans think that charting on billboard will be equal to Koreans streaming their faves.
I’m not saying it doesn’t help at all but read the second paragraph; UNLESS is something so big or never being done they don’t really care enough to check out the song/album.