In chapter 34, Jin Yong said the Xuanming Elders' lightness kung fu were not First Class. Even normal fighters at the Mongolian camp had better lightness kung fu.
And yet, in the same chapter, Jin Yong wrote (see bold part):
“张公子救我,张公子救我!”张无忌呼呼两掌,使上了十成劲力,将
玄冥二老逼得倒退三步,展开轻功,向王保保马后追来。玄冥二老和其余三名好手大惊,
随后急追。张无忌每当五人追近,便反手向后拍出数掌,九阳神功威力奇大,每掌拍出,
玄冥二老便须闪避,不敢直撄其锋。如此连阻三阻,张无忌追及奔马,纵身跃起,抓住王
保保后颈。
How can they be nearing Zhang Wuji as they run, when Zhang Wuji's qinggong is much better? The distance should only get wider.
Also in chapter 9, Jin Yong described He Biweng's lightness kung fu as very good (极高), such that Yin Susu had no hope of nearing. Possible contradiction to the "not First Class, even lower than a couple of ordinary fighters" description later?