I guess if you call someone a motherfucker in chat, that goes against the rules but it isn't cheating.
Yes in that instance i agree - that is abuse not cheating.
However if a site states that discussing your cards while the hand is still live is against the rules then the site would view that as cheating - same as colluding.
If he was actually telling the truth and he did have KK then the two of them are colluding because he is telling the big blind what he is holding so that the big blind doesnt call and risk being eliminated.