....it really bothers me that the ex and the current bf look literally identical

don’t overthink it. the author said in a Q&A that Jinhyeong has a type (i can’t find the link cause it was sent by someone else, but if any kind stranger happens to find it, that would be great :)). that’s the only reason they look like. if we have to make a parallel, despite looking alike, the way they handle Jinhyeong‘s CPTSD is different.