Thank you for your message, Saigc.
I know there is confusion between H-1 visa and EAD when an I-485 petitioner uses his EAD. But EAD of AOS is just employement authorization for the I-485 petitioner whose application has not yet been approved. My wife did extend her H-4 because I renewed my H-1 visa. Usaully "renew" equals to "extend".
For H-1 holder, if you want to keep H-1 status, you cannot use your EAD. If you use your EAD, you will not use your H-1 and the H-1 will be automatically lost. Because H-1 is a temporatory working permit for the beneficiary to work for the petitioner, a non-immigrant work permit. If you don't use it, H-1 will be voided. Remember one can not keep two type of work permit. But for H-1 whose I-485 is pending, actually there is dual status, non-immigrant and immigrant.
For the spouse of H-1 (H-4 holder), you can not work by H-4, but you can work if you get EAD due to I-485 pending. It is not contrary for me. If you can not use your EAD, just stop using it. Your H-4 is still there, because the principle applicant (your spouse) of I-485 is still keeping H-1 status. Because during this period, H-4 holder doesn't have two type work permit. I think there are some difference between H-4 and H-1 when they use their EAD during the I-485 pending period.
Saigc, I am not sure if you are a lawyer. If yes, just tell me you know the legal source. Here, I think, we need to know how the immigration law regulate such matter. Where is the legal source of "If one H-4 started to use EAD, s/he will no longer be in H-4"? There is a example, the spouse of J-1 (exchange scholar) can apply for EAD and use this EAD to work. S/He is still in J-2 status if J-1 is still valid. If his/her EAD is rejected, s/he just need to stop working.
The above are my understanding about this kind matter, professional advices are appreciated.
James_Dick