1979 was the year the story in the book took place, the author said in the interview she was 6,7 back then, in the next sentence she answered that she saw the parade of prisoners when she was 5,6.
From the brief description of the book, it sounds like she based her story on the execution of 钟海源, who was executed as a political criminal in April 1978 and had her kidney taken out to be transplanted before the execution. This much was accountable based on available memoirs and news reports.
Why the author set the backdrop of her story in 1979 is questionable, this particular detail was not brought up in the interview. I have no interest in defending her mistakes if she made one, but up to this point there's no evidence that she shifted the year intentionally (just to make a mistake?) in the story, we would have to read it to find out.
thanks for reminding me of the story. It's tragic.