[Wrana]

Considering Ermor LA/MA. As far as I understand what KO said (especially about more periods), MA Ermor was actually a probably very short period of time before catastrophe which lies somewhere between EA & MA, while LA Ermor lies in MA. With no Ermor nation at LA - just a desert with no life.
Another thought was that some nations (such as Hinnom, e.g.) lie further in the past than others - which would also explain why they had less tech at LA...