The purpose of stamp is to use as a card till you get your card- which is right. Even when you travel with your stamped passport you still need to go for a separate check at the port of the entry similar to the one you go thru when you travel on AP. I have travelled both with AP and a stamped passport(without AP) and the procedure was the same except the standing queue was different.
My passport was expiring in 4 months time when I went for stamping and INS officer told me that you don't have to have a stamp on your passport and you should get your card in 3-6
months time. Incase if you didn't get the card by that time you can comeback with your new passport and get it stamped, but I requested I need to have the stamp as I was going out of the country on the same day for an emergency and got it stamped. At the time I asked in detail about the procedures of the stamping and finger printing. I was told the officer that you don't have
to have stamping on your PP to get your card. What we need to process your card is your 485 approvel, two photos, and thump finger print. If your case is approved they will look the details and just take the photo and finger print. Other documents(such as I-94, EAD , AP previous H1-B all are optionals to submit). They can track your details based on 485 approval.
Now incase you don't have AP and EAD, I think they must stamp on your pp but if you have this documents they may not stamp(based on case by case). However you have all the rights to ask and get cleared why they are not stamping on your pp and they should explain to you. As far as you are working on H1-B (assume you don't have EAD) and once you are approved 485 (eventhough you have time in your h1) you are out of H1-B visa status.
Based on the information provided early
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The interview officer just went through I-485 and asked me a few simple questions and the envidence of employment, then took all of the original I-94, asked me to take fingerprint and sign on I-551.
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Unless they want to order the card, they should not take your I-94 and fingerprint and also they should not ask you to sign on I-551.
According to me this case has been approved and he/she should get card in 2-3 months time. If it is not approved why should they ask you to sign on I-551? and also should not take your fingerprint.
Fingerprint(thump) is only required when they want to order the card.