[adastra22]

I wasn’t talking about translated docs.

There are whole stacks of software used in Japan which are not used anywhere else. Sometimes it predates western adoption of similar ideas (like the media phones Japan had years before the iPhone, which to some degree Apple was copying), sometimes it Japan that adopts something western and then forks it. It is a recognized and studied phenomenon: https://en.m.wikipedia.org/wiki/Gal%C3%A1pagos_syndrome

There is some advantage to speaking English as you then get access to two separate development cultures and can pick the best of each for the job. But it is not a hard requirement like it is for the rest of the world. Only a small minority of engineers work on the latest western technology stacks like we do.