Ref.: TOS episode “All Our Yesterdays.”
I wonder if the Sarpeidonians' Atavachron might in some way be related to the Iconian Gateway or some Transit System like that in the movie “Contact”? The Atavachron was a temporal portal, presumably manipulating space-time along the lines of the Iconian Gateway and the “Contact” Transit System. The Sarpeidonians chose not to use the spatial function for some reason, or used it in a limited capacity, just as the Iconian Gateway appears to have used only the spatial function (at least that's how it seems from the limited exposure to it in the ST 24th century).
Might the writers actually have had this continuity in mind?