For those who wonder they he refers to Kah as assasin/fighter:
*What is it that makes an assasin an assasin? *
the combination of quick burst and high mobillity, allowing to easily close in on a priority target, get of a quick burst, and then disengage till the next rota is ready.
*Does Kah fit here? Yes! *
His E alows to close in, the Q+W+AA+passive alow for a fast and strong burst, and if he gets the kill the E-reset gets him out again, if not his Ult allows to disegage aswell, and it can also be used to re-engage.
What does make a fighter a fighter?
Initial tankiness(or enough dmg to built tanky and still be a huge threat), good singletarget dps with burstspikes, high sticking power due mobillity/cc.
Does Kah fit here? Yes!
His W heal and R-dmg reduce give him alot tankiness, and the %dmg of his Q aswell as the overall high dmg allow him to be a threat with only armor pen, so he can go tanky if needed. His E + passive slow + W slow + Ult speedbuff + more passive slow grant him insane stickiness, his low cd Q and up to 4 passive procs in short succession alow him for high, spiky singletarget dps.
So Kah fills the role off a fighter and a assasin at the same time, he does not have to realy choose, just like old rengar, so why does rengar get (rightfully) reworked, but kah stays untouched if working hybridclasses are BS(quote in the original post)