i think it has sth to do with superiority/domination (by age and consequently life experiences) when it comes to intimacy but in general it reflects closeness so both meanings fall into an affectionate authoritative category where the bottom is basically giving their body/control to the top/hyung and that's quite a turn on at least i see it that way ^^ m
As an Asian person who also has the equivalent of “hyung” etc in their language, it’s bc that’s what you usually call someone older than you that you trust. It feels rewarding when you get called that bc it’s like the other person is saying they rely on you with that title alone
I always wondered why tops get excited or aroused when bottoms call them "hyung", I still don't get it