Actually, this question is easy to answer. If he is a big enterprise, it is not surprising that he has branches all over the country. If Huzhou company is currently being established and there is no personnel department, it is possible that Shanghai company needs to recruit things. Or, it is very likely that the Shanghai company has a work project in Huzhou and needs to recruit a long-term worker in Huzhou.
We can't judge whether this company is an informal company by this alone. Whether it is true or not, only when you go to the company for an interview can you draw a conclusion based on your own questions, the interviewer's answers and the company's environment.