Yes "b-side" just means that they are all the other songs on the album besides the title track(s) that are heavily promoted. I wouldn't call them "fill-ins" though....because to me, that implies "afterthought" or "placeholders" and has a negative connotation. They are often the songs that are the most creative, and that aren't looking to meet the precepts of commercial appeal. For me, b-sides are often the best part of any given album. So when those "antis" call this song "b-side material" that isn't the diss they think it is. 😂 I agree with you that it's nice to see artists stretch their wings. The reason HYBE groups are doing so well is because their writers/producers/artists are encouraged to step outside of their comfort zones, try new things, etc. It's in the company DNA starting with Bang PD managing BTS in that way from the get go. It's what sets BTS apart and makes them "more than K-pop," and a lot of the other HYBE groups are heading down a simlilar path. It doesn't mean they will reach the same success, because BTS is special in a way only they can be/do. I say all of that to say I really like this song, and I'm a big fan of Le Sserafim, whereas I can mostly leave (as opposed to "take or leave") pretty much any other K-pop girl group. Le Sserafim is great - strong dance, creative, great messages. I always share new BTS/Le Sserafim music with non GP friends and family - this one has made some noise with them. They like it.

Check out this song - "Laal Peeli Akhiyaan" it is fun dance number, not Hrithik but pretty good dancer.