My memory is fuzzy, but it was something like "Kai looked at a few of the boosters in a practice draft, and then was able to tell us (something) about the cards that should be in the remaining packs just by reasoning about print sheets."
I'm sure I'm getting the details wrong here - I'm not positive that it was Kai, and I don't have a good enough mental model of print sheets to know what was possible back then. And I think these skills aren't relevant today (?)
But I thought it was a fascinating detail. It's always fun to hear about the wrinkles that serious players of a game pick up on in order to find an edge.
(I've searched for the story a few times and haven't been able to find it; I just don't remember enough about it now)
edit: some discussion below, but I think the story here is approximately "Kai memorized all possible print runs, which was feasible to do back then, and was therefore able to back out which cards had probably been drafted and who was probably holding them" or something like that. Nothing about reasoning about runs across boosters!