It was a very big deal. At 2009 Worlds she set the world record of the short program for the 3rd time in her career. The first time she made it it was Worlds 2007, where she got 71.95. That was an incredible score back then. I guess it was the first time when Brian Orser sat with her in the k&c and as a new coach he didn't really know what was the world record score then, so Yuna was very surprised and happy when she saw her score while Brian smiled a little but he didn't even realized what was going on
The second time was 4CC 2009, where Yuna got 72.24, then only 1,5 months after she set another world record at the World Championships, 76.12. That score was monstrous, not only her skating but also the scoring itself set ladies's figure skating to a completely new level.

I think I have never seen Yuna happier and more carefree in the k&c than she was after SP at World 2009.
Between Vancouver and Sochi, no one could even come close to Yuna's world record she set in Vancouver. The only one who could go the nearest was Mao at the 2013 4CC (74.49), but it still wasn't anything near to the WR.
Since Sochi, everything changed about the scoring, it is now way easier to get higher scores than it was before.