This has really been bothering me....but why is there a noticeable chronological gap in the Dragonborn prophecy between "when White Tower falls" and "when the Snow Tower lies sundered?" The prophecy first lists off the events at the closing of the Third Era, then skips 200 years to the Stormcloak Rebellion while ignoring other important events in the Fourth Era like Umbriel, Void Nights, and the Great War.

Yes, I know the individual items refer to the events of the numbered game installments, but it feels very disjointed in the context of Tamriel's chronology. Especially since Void Nights sounds as mythically important as Nerevarine Prophecy and the Oblivion Crisis.

The Void Nights didn't feature such mythic events as a Tower being disabled. That would be my best guess.

Because they wanted to skip it for whatever reason and visit it later, if ever, down the line.

Not all important events have to be directly related to a prophecy. And unrelated events can certainly occur in between those major ones we're looking at. I don't think it is fair to lump the great war in this category though. It's the reason the last line of the prophecy is fulfilled after all.

Here's an interesting question (to me anyway); Was Alduin always going to come out of the time wound at 201 Fourth Era or was his arrival explicitly tied to Snow Tower being sundered?