I just got this from USCIS website
Chapter 45 Waiver of Section 212(e) Foreign Residence Requirement.
Note 2: A “no objection” case is the only situation where the alien is allowed to file an adjustment application concurrently with waiver request.
Now I know why most lawyers told that I485 could be filed with DOS recommendation letter.
So my case should not be a problem! Wanna share this information with you all!