Technically, the validity of H4 EAD is tied to the H4 holder’s status. I have not seen a situation like yours before, so I don’t know the right answer. But, my two cents, do check with your attorney. In my view, you should be able to use it, as soon as your H4 status is active. The employers will use your H4 and h4 EAD card for I-9 compliance…
As I said, please double check with an attorney before you puruse this. Also, do update here for community benefit.