Nevertheless, as I said before, my nephew's account of what Williams said later has been seriously undermined by the evidence you presented. Therefore, it is legit to wonder about the rest of his narrative too. He is a good kid and I trust him. But even good kids can fabricate or inflate narratives.
If your nephew's account is wrong then either he played you or Williams played him.
Thinking this through, would your nephew have pranked you with a story replete with details and hewing to a common line of recruiting cheating? Would he do that? Is that in his nature? And why would he do it? Just to set you up and watch it play out on the internet?
Quite frankly, your nephew's story sounds reasonable. If fabricated, it's flat out a lie. Your account of nephew's character doesn't fit the fabrication angle. It's easier to believe his telling than to believe it's a lie.
The inflation angle doesn't work very well either. The story is too simple to inflate. At the story's core is the quote, "Nearly zero." It's pretty hard to inflate, say, "50-50" to "Nearly zero". No, that would be a lie - see paragraph above.
Absent better knowledge, I'd take nephew off the hook.
Did KW play him? Who knows?