what BTS video Casa studios you talking about?
whether your over thinking or not, if he really has crush on her that's not weird. i mean i'm a woman & i'm also have a crush on kim. so what is so weird if a guy who had interaction with kim has a crush on her?
there are many other actor who's fallen with their costar while shooting/filming together
with many kiss & intimate scene between them, it's not weird if James develop some feeling towards Kim LOL
but i'm ok with whoever Kim like. it's her life after all.