Yup. I noticed it too. Its like Eldians are more on Norse myth and Marleyans more into Hellenic because of Helos i think. Ymir is actually the 'father of all titans' in Norse myth and almost similar that he was eaten.
I think that has something to do with how the SNK will end. The place where you borrowed the power is where you return it too.
So i believe that it is Eren's job to save Ymir and the world by bringing all 9 titans to that tree. But of course, with the author's twist.