If we saw the Sahagin homeland on the Source, I bet SE would include one or two relics as a wink-nudge, but ThE TeSt oF TiMe and seven calamities have probably demolished most of what's left of Source-Amaurot into dust, while there might be intact ruins here and there on the shards. Think about how much the land changed just between the Sixth and Seveth eras. Honestly the fact Limsa and Eulmore's foundations are so close is something of a miracle. Or the result of conveniently repurpose-able modeling assets. Or a miracle!