It's way too early to splinter off a new timeline into even more, new, "Parallel" timeline. Yet.
Yes, after a solid seven years each of new stories.
Why not? The movies have their splinter timeline, why can't the novels have their own one, too? Especially since the novels aren't allowed near the movie one.
We know how it all ends, all there is is to fill in the gaps. And we're at the point where they're all packed solidly and we're getting the fourth or fifth "end of the 5YM story." Doing an ongoing TOS Myriad Universe can not only cash in on the current movies but give longtime lit fans something fresh and exciting with TOS characters.
But you are asking for a "Myriad Universe"
based on the new movie (ie. releasing the four shelved novels now) that won't necessarily agree with the next new movie. And Bad Robot doesn't want that kind of story tie-in being published. For now.
That's not what I said. My only mention of those four STXI novels was just the usual "Oh, I wish they'd release them one day" and seperate from my suggestion of a new TOS Myriad Universe-style novel series, where anything can happen to Kirk and co.