But wait! I have more things!
I have been watching the Clone Wars, and I'm in season 6, episode 12 where Yoda is learning how to become a force ghost.
Now he has a vision of what happens, basically he sees that all the Jedi are dead. The two that are focused on are Mace Windu and a Padawan named Petro. Then we see Ahsoka who is not quite dead (because there is always someone who explains in the vision that explains what happened). Yoda speaks to Ahsoka and she tells him that the Sith killed everyone and then, well, she dies. This is something significant. We know that Petro dies, because he does die during Order 66. Ahsoka... Doesn't. She hasn't died in the Mandalorian yet, but we know she will as we can hear her voice in Rise of Skywalker. But since Petro was seen dead and does die, that means that Mace Windu did die during Order 66.
Like in Avengers Age of Ultron, Black Widow is in almost the exact position she is when she actually dies. And Cap (since there has to be a person that tells you what happens) isn't, because he doesn't die, he just grows old.
So yeah there's my theory