This is good for a person who isn't really professional. A foreigner saying they are an English teacher for example, they know you're not actually a licenced or certified teacher with the relavent responsibilities. A Japanese person in Japan can simply say they are an office worker or the like for example, whereas I would say specifically what my job is because they would otherwise assume I wasn't in a career. Japanese people don't take foreigners seriously, which is a major cultural liability. Foreigners really need to go the extra mile if they are not stereotypical, becauuse the assumption is that you're not in Japan permanently much less a real professional. If a foreigner lives in Japan permanently, they need to say where they live, not where they're from, the same as we would if were foreign born residents in any other country.