Attack on Titan Requiem

I am confused, in Attack on Titan Requiem, Eren was showing his younger self memories of the future and made him forget the memories and said u will gain em back on that day(Medal cermony day). But in Attack on Titan season 4, Eren says he saw the future through his dads memories of him showing his dad future, and if thats true, how did Eren made Grisha see the future when Eren hasnt even experienced that future? Cuz Attack titan can see the memories of the future holder only, right? So Eren couldn't have been able to see his own future memories, so that makes me think Requiem is right, but then again, Eren said he saw the future memories thru his dads memories