Please refer to wording below, it indicates J-2's EAD is invalid upon J-1's not being in such status, which is different from above specific case though.
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How long may I work? J-2 dependents with employment authorization may work until the date on the EAD card or until the J-1 principal visitor completes his or her program, whichever is earlier. J-2 dependents may apply to renew work authorization, as long as the J-1 visitor remains in status.
May I still work if the status of the J-1 ends? If the J-1 visitor discontinues the program at Columbia or changes to another visa category, the work authorization for the J-2 dependent will be withdrawn. Legal work authorization for J-2 dependents is always dependent on the status of the J-1 principal.