I just saw this tweet, and it rings true. I can only think of 3 other artists in Gaon history to do this: Busker Busker, BIGBANG, and IU (who's charting 6 singles + b-sides right now).
And before someone tries coming for me, no, I'm not saying that all of the songs will become "national hits" (3 of them already are). I interpret this to mean that BTS is one of a select few acts that can reliably chart multiple songs and has many songs with high levels of public recognition and success.