I disagree. McCoy went back in time and altered history and thereby altered the timeline.
But again, this is fine. You can disagree. But your opinion is not fact, nor is it Truth. It is an interpretation based on available evidence and how you choose to lend weight to different testimonies and exhibits. For example, I do not lend any weight to George Lucas’ revised interpretation of the Original Trilogy (read: Special Edition). I do not lend more weight to the theatrical edits of the Prequels than those made by fans just because they are labelled “official”.
I want to appreciate and enjoy the Prime Universe, and I therefore lend more weight to evidence that it still exists. You don’t have to, but you also don’t have to tell me that I shouldn’t in a manner suggesting that I am otherwise wrong.
Again, my doing so is not contrary to the Truth because this is a work of fiction. I understand that Truth is not actually left up to interpretation (ie. God exists whether I believe in Him or not), but that’s not what we’re dealing with here. There is evidence to support either argument and you’re free to choose what your interpretation is.