No, it is not “obviously wrong”. “They” can refer to a single person of any or undetermined gender.
In this case, Satoshi is a Japanese male name. If you have evidence to suggest otherwise, there is no reason to pretend you don't know the gender.
However, in an article in which you speculate about the real identity behind a pseudonym, suggesting any possible gender or plurality, you should use /they/, this being the whole point of what your doing.