I just got an update from FO. IO confirmed that she sent the info to the embassy a couple of minutes ago. So, in conclusion, is not the FO who triggered FTJ, but most probably the embassy itself. In one of the emails, they mentioned that they checked me through USCIS system (something internal I believe) and my status wasn't updated yet.
So, my advice for future AOSers who will do Follow to Join - work in parallel with embassy and FO. First, try to ask the FO to notify embassy about your approved case. The embassy needs just a confirmation to start the process from their end. Second, ask embassy to verify you through their system, they deffently have this tool, they need just to want to do it. Finally, as Sm1smom said, no need to file i-824 and pay for it. I did file, pay and I lost my money, but I don't regret because considering that the time wasn't on our side, I was pulling all the strings I could, and for some of them I had to pay (including consultations with lawyers - this one I regret)...
By the way, my status just changed to approved
Congratulations! As a DV2021 AOSer who is planning to do FTJ for my spouse, I have been caring about your progress. I'm truly happy for you that your GC journey is successful and your wife is able to have an interview date set.
I have questions regarding civil documents submission for you though if you don't mind. Mom has suggested me to submit my husband's civil documents regardless of whether KCC requests them or not. I'm curious if your wife received the email from KCC to request documents (if so, when did that happen?). Did your wife send the documents anyway?
Thank you in advanced!