About the Family D's situation (and a bit about millsage)

⚠Spoiler Warning (Recommended for those who have finished reading both bands) After finishing the story, I felt "It was good~~", but then a question popped up. Wasn't the reason why the Dumb Rock family became a twin vocal group not mentioned? They did say something about Miku compensating during an in-house live performance where the song playing was chaotic, but that seemed more like the guitar was the main focus, not really twin vocals. (In fact, millsage touched on that more). Will the story unfold with them deciding to become twin vocals from now on?