It has more to do with the arena than the shuttle. But I think the heat and the atmospheric pressure changes the speed of the shuttle from arena to arena
BWF should change the slow shuttle to faster shuttle. If not I'm afraid that a lot of top players will be exhausted in World Championship tournament.
Yamaguchi aiming to get her 11th SS tomorrow. Starting to rake it up. There was once that she keep losing in early rounds and you wonder what had happened to her. Tai Tzu Ying has 22 while WangYihan has 20 i believe is the frontrunners.
The opposite, heat (and humidity iirc) make the shuttle faster, they probably went with a slower shuttle speed because it was warm and then turned up the AC a bit more