they just stand less risk if they mistake a Vietnamese for a Jap, but they DO NOT know WE CHINESE dislike that---when my wife and i took a pic in a garden, a looking-decent mid-aged couple asked :"Ni Hon Jin?", I happened to know this=Jap, i said, "No, We are Chinese, they are our enemy", they became a bit amazed and SOON relaxed coz they have been both jp and cn, and they knew we do not like jap.