This song would be perfect for back and forth vocals with Adam and John. Just listen to the "I'm sorrrrry" and "Come baaack" and you can totally imagine John repeating the parts. Missed opportunity, but it's still an amazing song. 
yeah it's proper weird, cus every time i listen to it i'm always expecting John to echo Adam's parts, even before you said that. really surprised they didn't do that. there's not enough John on the album for me but i'll live.