I’m curious to see how the show approaches the timeline implications of Una staying on the ship instead of getting locked up in a penal colony. I hope they throw in some tidbits about it, preferably as a running gag. For example, she ends up doing another enterprise bingo that Kirk admires or something. Maybe an episode where they have to go that penal colony and she gets dejavu or something. Like Olivia from Fringe type of dejavu
The prime timeline is the one when she was acquitted, but in the “Quality of Mercy” timeline she was sent to a penal colony.
That wasn’t the Prime timeline, though, or it never really got the chance to be for very long - that was the timeline when Pike decided to write to the kids and avoid his fate. So while a butterfly effect may have ended up having Una still incarcerated, that wasn’t what we wound up with, not at the end of the episode, and not in “Balance of Terror”.
Having Una have temporal shivers from a timeline that no longer exists would be a neat idea, regardless.