My first thought was that it was lie but... I don't know how to read this show anymore.
I read a quoted portion of an interview that suggested that GRRM gave three pieces of information to Weiss and Benioff after they burned through his source material. First was Shireen's Death, the second was "Hold the Door" (which makes me tear up a little), and the third is something that happens in the last episodes of the show's story.
Otherwise, I think it's going to be really interesting to watch the show fumble with the story as it stands - because ultimately I don't think Weiss or Benioff are as good a writer as GRRM (and I didn't like ASOIAF when I tried to read it as a teenager, though GJ has recently sparked my interested in reattempting, as Wilshire did for me regarding Malazan).