Curious to know how this will affect immigrants who arrived on a student visa, receive OPT to stay while working, and then subsequently get married. I know many top performers at my company who are in that boat, especially from India, who have built lives here during their OPT + STEM. It would be a shame to lose them if they have to go back to India and wait years (if not decades) for a green card or H-1B.
No. This is the last stage of the Green Card process. When you do Consular processing you make an appointment at the US embassy or consulate in your country, go do the interview and then you are granted the GC on the spot. Then you fly back. You don't need to fly back for years, it's only for the purpose of the interview at the consulate.