Q: [instrumental melody]  "hello and goodbye" great. this is you replying to your past self, in the same way your past self called out to you-- you havent changed in the little ways
A: the actual explanation for this line here is much more simple. it's just the same as it was before, because it's been established that that's how the song goes already. i'm commonly guilty of altering too many lines from chorus to chorus, and not having enough things repeated the same. but in this case i was able to keep it inside the box