And you all thought Prince Ami was endgame when the real prince was in Ami/Amy the second pants.
It's the first time you're hearing of it because it's a theory that comes straight from the last update. But generally, yes.
Now, mind you, regardless of corrupted realities, the people of the cycles are half-shadows anyway. They are the real them at the same time they're not. That could be because the real people are dreaming and what we see are fragments of their conscience inside a simulation, or because they are fragments of the whole cast adrift through multiple realities, we don't know.
Regarding the corrupted realities, we have enough evidence of multiple cycles existing where Sekai married Akira, or at least was alive. The Pareidolia mall reality has Amy having lunch with her mom after her boyfriend (Akira fell down the hole), in "arms bent back" we see them forming a family unit that is aware of the cycles, in the Happy Ending timeline (where Nodoka is murdered) we have a lot of detail as to how it came to be (Akira married Sekai right after "Kyoto"). I'm assuming that is generally how all of these realities started because getting married to Akira is what preserves Sekai's life, and she's alive in all of them.
Then we have the realities where Sekai is dead. Well, the difference between all of them is that when Sekai is alive, Maya doesn't exist. And when Sekai is dead, Maya is there. If we couple that with the fact that Ami seemed to have "Maya's place" in the cycles where Maya wasn't there, and the fact that Ami seemed to have been experiencing the cycles for much longer than Maya (the scary room scene in the last update), we can conclude that the cycles started from a reality where Maya didn't exist and Sekai was alive. Then, at some point, Maya started existing and the past got altered. I don't know if the past actually got altered, or it's just their memories of the past that did though.
For example, it could be that when the cycles stop, Sekai is just there alive, cause she never died in the first place (the first timeline being the real one). This is all very novel, mind you, because it hinges on things revealed during the last update for which we could certainly use more clarification.