Just read up on that story. I’m amazed they were allowed to give characters backstories when the show was still on, and that early into its run as well.
I'm guessing it was because Tasha had already been written out at that stage (the final chapter deals with the aftermath of her death) and they didn't anticipate visiting her homeworld and giving her a sister three years later; they probably still thought the show wouldn't last past season two, for that matter.