Dunno why some have major issues when Emet-Selch himself said we would be surprised by the civilizations in the other reflections and Alexandria is from the 9th Reflection too.
You must have skipped the dialog from MSQ when it was plainly told that it took four centuries for Alexandria to reach the state it is in from the days of the Storm Surge meaning their scientist have been studying for centuries to get to where they are today and for the dimensional fusion to occur. But you don't have a problem with the three centuries it took for Garlond Ironworks and G'raha Tia to teleport the Crystal Tower to the 1st and you with the Scions way back in ShB.