Just an idea... The writers said that since before season 1 started that it was in the prime universe.. but.. Since it seems Mitchel was killed on Vulcan as a small child by some beastie and only lived because the Red Angel from the future helped to change things. Did that shift the whole timeline from that point forward? This might explain why Spock never spoke of his sister in any other series (cuz she's long dead). Also Michael was partly responsible for getting the spore drive running by using the tardigrade. Without her it might never have been fully realized which could be another reason it's not in any other series. OR... is every show we have ever seen to date because of the actions of the red angel. So essentially we are seeing how the prime universe started and we have never seen the universe in which Michael died as a child and all the following consequences. There are a million other examples which I am sure you can think of to help or go against this though. Thoughts?