It's not relevant because adding music would have zero effect on your gameplay experience. You are literally the people who screech about optional content because the dev is 'wasting his time' on it.
From the perspective of people who don't want the content, or the music, it's valid to wish they didn't bother with it to make the parts you do want better, or come faster. One of the differences between this music discussion, and other times people have complained about optional content is: The Dev asked for people's opinions on it.
The Dev is clearly trying to find out how many people actually care about the music content, so people who don't want him to spend time on it, regardless of their reason, are valid to the discussion. If BrainDrop had just started adding music and people started complaining, it'd be different. If someone had started the discussion with "Hey everybody, just want to say, I think music is a waste of time, and shouldn't be in any of these games" it would be different.
In *my opinion* music isn't necessary in the game. If BD winds up deciding it's good to have, and puts it in, I'm not going to complain, but my opinion is still valid to the question he asked.