Is such a corporate overlord clause illegal?

Such a corporate overlord clause is of course illegal. However, China's laws are basically powerless against such minor violations. Unless you don't recruit according to its requirements, the behavior of the enterprise has brought you great losses, and you can rely on the law to get back some possible justice.

This kind of enterprise basically belongs to extensive management and can only make money by manpower at low cost. Relying on the strong market demand in recent years, there is no future. If you have some skills, make plans early. If you still want to work in the factory, you'll have to put up with it.

You can be reasonable, but how can you reason with an unreasonable person?