Everything has to be taken in context. Is it an old flag from a known address or a known school or factory, and are there verifiable people on the flag (a principal, a mayor, a factory owner). If so, and if all the language on the flag is proper and correct, then it doesn't matter so much of all the writing is the same - maybe some clerk wrote it on behalf of all the people.
If there is no verifiable location, date, or other identifying mark, and if the language is clumsy or anachronistic, or is peppered with Chinese-style reduction of the kanji, and it is all written with the same brush, one has to be very, very suspicious. In this case, the flag has a couple of red flags, plus it came with a suspicious translation, so the gut reaction is to assume it is a fraud.
Note it is just a gut reaction - the flag could indeed be authentic. But without deep research or access to military records, all we can give is our gut reactions.