First of all, the FOIA letter would never say "yes, we approved you because you submitted unsolicited evidence!" as that is not the purpose of FOIA 🤣.
Yes, it is on the "Case Flags" generated by the system. One of the transactions under "Adjudication" says "No I-864 appears to qualify". The transactions shows when I uploaded the file. The unsolicited evidence is part of my A-file under FOIA. Per USCIS in your portal "You may upload additional evidence that you believe may assist USCIS in adjudicating your application, even if the evidence was not specifically requested. USCIS will consider the timeliness and relevance of unrequested evidence when making a decision about your case." In my case, it was considered. I wonder if those people you are referencing have tangible evidence about what you stated. For me, this is a PSA out of the goodness of my heart just to share to people based on one real-live case. You can choose to ignore it. The main message is it does not hurt to upload it if you think it will improve your chances. I thought the same way but my thinking was, worst-case scenario they ignore it and I bring to interview. I never had an interview as they used it.