I'm not sure about the reference to saturn being the one that birthed earth. It just sits more right with my core that the sun ejected them all. Not to say I'm right, but if what we are told of Saturn being a gas giant, how does it birth rock?
Imo, I think the sun was responsible for all the planets. The difference between gas and rocky perhaps could have been different phases the sun goes through. Clearly the process would take years, so it isn't anything we've ever been able to study though and I certainly may very well be way off base.