Generally speaking, Gundam's assembly model, also called Gunpla, is a product of Bandai Hobby Department, all of which are produced in the Bandai Hobby Center Factory in Shizuoka Prefecture.
Other finished toys of Gundam, such as GFF, HCM, Mia and robot soul, are the products of collectors of all generations. These products are mainly outsourced to manufacturers in China and other places.
In fact, many people in China only have a vague concept of the so-called "Bandai", but they don't know that it actually has many different branches with different business scopes. So if you want to strictly limit the definition of "model" to "Gunpla" developed by Bandai enthusiasts, you are right.
If not limited to Gundam, Kotobukiya, another well-known manufacturer engaged in the development and marketing of plastic models for science fiction and animation works, is different from the business department of Bandai Hobby, and all their products are outsourced to China manufacturers.
Besides, you mentioned MG's red heresy. The MG red heresy of b society was released as early as two years ago. If the "latest" one is mentioned, it is a brand called "Daban" copied in China. There is no doubt that it must be made in China.