Eregion is an Elven realm with the main city being Ost-in-Edhil. Again, the whole realm of Eregion was founded according to the writing of the original lore was to be a bulwark against Sauron in some accounts. And it is to that city, prior to Sauron's presence and location being identified, that he traveled in disguise as the Elves were not expecting him. That made Eregion the center of the story in this era of the 2nd age and once Sauron was exposed as Annatar, he laid siege to Eregion. So all the elements of Elven defenses against Sauron, Sauron's trickery and deception in hiding his armies and the creation of the rings of power all centered around Eregion.
This tower in Amazon's story is an alternate location as a focus for their narrative as there is no Annatar and the forces of Sauron are not far to the south to keep from being detected. They are relatively close by the tower and thus ultimately detected so as to create a new flashpoint or center point for the conflict in this story separate from Eregion. Amazon is making their own version of the story and it is not going to follow the story as told by Tolkien. So obviously this tower and the human towns are supposed to be a focus of the conflict which is why they have this elven commander to act as a placeholder for Sauron. Otherwise, compressed timeline or not, there would be no need to have this tower as the focus because the story would simply be about Annatar infiltrating the Elves at Eregion.
You haven't disputed this and the show itself is telling you this. If Galadriel is going to war with the forces of Numenor they will be going to war at the tower not at Eregion. It is obvious that is the intent here. Eregion and the rings of power being created is likely going to come much later in a later season.