Oh, now I see what you're saying. Ok, you're right, to be pedantic, the original phenomenon should be reworded: Whenever 6+ kids get together, either there are 3 mutual friends, or there are 3 kids K1,K2,K3 such that for any two K_i, K_j, either K_i is not K_j's friend, or K_j is not K_i's friend. I was implicitly using "A and B are friends" to mean "A is B's friend, and B is A's friend". Thanks for pointing that out :)
My bigger point was that the literature on any given topic is chock full of discussions like this. Is friendship directional? Is it binary, or does it make more sense to consider weights on these edges (casual acquaintance/best friend)? Can an outside observer infer friendship, or do you need to rely on self-reports? If so, how consistent are they? And so on.
The more patient researchers are happy to walk you through these sorts of considerations, especially when you're introducing them to a new tool or something. However, if you catch someone who's busy—or grumpy—you might get blown off with "That won't work. Haven't you read the literature?" Personally, I think this happens too often, but you can sorta see how people might get sick of regurgitating the same arguments over and over.
This is not to say that "read it and come back" can't be used as a moat, or that ideas "from the literature" shouldn't be revisited and questioned, but I think insisting that people do a bit of reading is not usually meant in bad faith.
