exactly he has lost all feelings (romantic) towards hyeonwoo
Yes, this is so important to his growth. He's moved on from HW and truly puts Jun as the love of his life however, Jun is still insecure about the past(in which subin couldn't move on from HW) and doesn't fully trust in Subin's love
I like how much he changed it's good they are not 19 year olds or something, even if I say it Jun is perfect person who is actually better to spend rest of your life a person who you can look up to, mature not hyunwo who is still crumbling in past with meanie behaviour that he would show he hasn't grow up at all only thing that has grown in him is fame , may be subin character developed more cuz of staying with jun which is good.
I think the fact that Subin kinda acts slightly indifferent with Hyeonwoo shows how much he's grown.