This step for China platform is usually not necessary.

China platform provide a weak account system that allow players log into game without registration.

(System will assign an account automatically)

But developer still can create Sandbox account to test Switch Account function.

A Sandbox account ,or test account, is required when testing games in Sandbox. 
Each partner is enabled to create a Sandbox account and test one game developed by the identical developer. 

How to create a Sandbox account?

1.Login the Developer Site with partner ID.

2.Choose “Account” > “Add Sandbox Account” in the left menu to enter the page for creating accounts. Input the Sandbox Account Name and E-mail address then submit.

3.Filled E-mail will receive an activation email with the URL about Sandbox testing for smart phone.

4.Click the link to active the account.

5.Finish the registration and the Sandbox account is created.