Really bizarre situation ... AOS approved before PD becomes current

[Vegemiteobsession]

Hi, I filed F2B AOS based on approved I-130 petition  last year June 2020. Currently 26M, Rest-of-World.  I have been in the US on F-1 without any breaks in legal immigration status. This is my timeline: 

August 7 2015 - petitioner filed I-130 for me as child of LPR (F2A) via a lawyer. I was under 21 then.

Dec 10 2015 - i-130 approved.

June 2016 - found out that USCIS elected to use Final Action Date chart instead of Date for Filing (remember that Date for filing thing started just around October 2015).  This month was the last month that I would count under 21 with CSPA, and after inquiring USCIS through congressional, I was told to file as F2B since I aged out and no longer F2A. Apparently, a lot of people went through this problem as well according to Visajourney. 

June 2020 - PD becomes current by Date for Filing. Filed AOS with a different lawyer.(also moved to different state in 2019)  

Jan 2021 - biometrics 

Feb 2021 - Interview done. IO stated that because Final Action Date F2B cut off date of February is July 15 2015, my case would be on hold until PD becomes current. DoS already published March 2021 bulletin, whose F2B date was July 22 2015, so we knew that my case wouldn't be approved. 

March 12 2021: EAD/AP combo approved. 

March 24 2021: Case was approved

March 31 2021: card came to lawyer. We then remembered that because my PD was NOT current for March 2021 (but would be in April 2021, whose cut off date is August 8 2015), my AOS approval may have been accidental. 

April 10th 2021: Put congressional inquiry to USCIS. 

April 15th 2021: Response came to the Senator office that DoS approved my visa number on March 4th  and USCIS field office approved my AOS on 24th. My lawyer and I decided to inquire again. I managed to get a hold of USCIS officer and get an appointment at the field office for next week.

I am really frustrated because everything went so well until this point...you know how we complain that USCIS does stuff so slowly? Well, they managed to mess with my life by doing stuff too fast this time. I haven't notified my DSO yet, nor did I use EAD/AP either since I am a grad student. I have scoured all over the internet to see if there was any similar cases, but there was very few, and they were all employment-related. My lawyer is also confused since she has never had this happened. 

Also, the green card states that my category is F27, which IIRC, is "child of LPR under 21". Shouldn't I be F29, "unmarried child of LPR?" 

If anyone has experienced this kind of mess before as Family Preference AOS applicant, please share your experience. 

Note: I one time talked to a tier 1 agent about this, and she told me that for AOS applicants, it does not strictly have to be based on visa bulletin. My lawyer thinks the agent is wrong, and tbh I think so too since I have heard far too many stories about incorrect information from tier 1 agents.