Sure, maybe Sera was an unreliable narrator, and it's just the USS Relativity working in the background to correct things (even if they end up happening a few years off from when they should).
But maybe in the time scale of millennia, it more or less evens out.
Khan comes to power later in the timeline, but DIS and SNW seem a little more modern than they should? Some things are slowed down, and others are sped up.
Why did they have to show Khan shifting into the future just one year after Picard and co. travelled back to the same time and we saw Soong on trial for the Khan project (a past event)? What benefit is there to jacking around with what they just established?