Ke Zhen E's presence in the Iron Spear temple

[pannonian]

Wrapping up their story from LOCH and revealing the truth of his father to Yang Guo at the same time, Jin Yong cleverly ties these plot threads together. The irony of these figures who were present at Yang Kang's death 36 years ago, to be present at that very same temple 36 years later. From Chapter 37 - Gratitudes And Grudges Over Three Generations:

A few tapping sounds were heard and the Flying Bat Ke Zhen’E walked in
and said, “Ke Zhen’E has kept his word and has come. These are the “Nine
Flower Jade Dew Pills”, altogether there are twelve of them, which makes
it three for each of you.” He threw a small bottle over to the bald man.
He said happily, “Many thanks.” and caught it. Ke Zhen’E said, “This old
man has completed his business and is here to die.” He was standing
erect proudly in front of them and his beard was floating in the wind.

The man with the lump said, “Shi Ge, he brought us the “Nine Flower Jade
Dew Pills” which can treat our internal injuries, moreover we don’t have
any deep feud with him, let’s just let him go.”

The skinny man laughed, “Hey, Brother Hou, don’t let the tiger escape
back into the wild. Your kindness may cause us to die a horrible death.
Although he hasn’t revealed our secret, how can we be sure he’d never do
it?” He shouted, “Let’s act together!” The four people rushed over and
surrounded Ke Zhen’E.

The old man said hoarsely, “More than thirty years ago, all of us
witnessed Yang Kang’s tragic death here, who knew it would happen to you
too; this is retribution.”

The question is: how the hell did they know Ke Zhen E was at the scene 36 years ago? After Yang Kang went mad from the poison, the Jin party sped off, leaving only Ouyang Feng and Huang Rong. It was only after Huang Rong's trickery that Ouyang Feng revealed that he knew Ke Zhen E was there all along, by which time Wanyan Honglie and co were long gone. Was this a Jin Yong brainfart, one that would make Yang Guo "hold his head with both hands in grief and indignation"?

[kyss of the sword]

ke zhen E' might have mentioned it when they set the meeting place as iron spear temple. or the jin experts might have been referring to their group only.