The controversy isn't really the "misleading" in general (because if it was truly meant to be a red herring and actually well executed, there wouldn't be a problem...but it wasn't, lol), but rather following it up with saying that the fans (with common sense, not just NS fans) "read the manga wrong" and therefore insulting a huge portion of the fanbase by basically passing off his now-obvious ineptitude and inability to plan, to stick to the guns of the story, and so on, onto those fans as if it's that portion of the fandom's fault the story turned out so badly (when it was the NH fandom, SP's bias, and, again, his own ineptitude) is what really burns people up. It would be like if Michael Bay blamed the Transformers fans for Revenge of the Fallen being such a bad (Transformers) movie.
And in terms of NH being "planned/decided", the most specific he got that I recall was actually during the earlier interviews after the manga was done, where he said it was decided only three months before the ending (which would be believable and help explain such BS, if only a tiny bit)...only to change it to "since the beginning" literally the very next week in another interview.
I was talking about the controversy that the interview and Kishimoto were referring to.
Could you provide a link to where he said he decided only three months prior? I don't recall that, and really, he would have needed to decide on nh earlier in order for the The Last to be written (or have nh decided for him).