It's pretty rich she describes all of this as her father's creation. Stan was always good about claiming all the credit, seems like his daughter isn't far off from that.
I've seen the theories but they're pure speculation....I really don't think it goes back that far. That said I loved the movie and was fine with the reveal.
I believe he was looking at using them as a stand-in for mutants since they didn't own the rights. I think now that Marvel/Disney has those rights the Eternals will fade into the background.