shoulda been "2 bids too far" - with a 6 count, responder's prime duty is to limit his/her hand at first opportunity, so cannot do other than choose between an immediate NT playing 6-9, or weak preference when offered a second suit by opener. The use of the unlimited 4thSF in my system at least would promise a game forcing position over two unlimited suit bids by opener, so could not be made on less than say 11 or more well-placed points.

but never mind, responder has grasped the basics of the game: "It's *your fault, partner!"