Shouldn’t the original timeline be earth-1/ earth prime?

I have wondered about this for a long time because (in what I assume is the original timeline) thawne didnt kill his mom Barry was a csi and then in I think 2020 Harrison wells made the particle accelerator and so on. And I was just confused because if every universe/ earth-# is created because a different action was taken than in the original timeline shouldn’t that timeline be earth 1? Not the his mom is dead and eobard makes the particle accelerator earlier.