The Department has informed the MIA (Migration Institute of Australia) that:

… the same arrangement continues to apply for family members (secondary applicants) of Subclass 485 visa holders. A person who previously held a Subclass 485 visa as a secondary visa holder is not excluded from applying for, or being granted, another Subclass 485 visa as the primary applicant.

The Department will clarify this further on its website shortly.

As of 1 February 2021.