Because he would have us believe it was all a red herring.
NS was way more then a red herring, even I would even admit that Taiora could be reasoned as a red herring, but not this. Way too much went into this, its psychotic if he did all this to keep a portion of Naruto fans to keep up.
He said in one of the interviews he purposefully made Kushina like Sakura to "mislead" fans. Basically he said he developed NaruSaku with parallels and all that just to pull a twist at the end with NH and SS.
Now some people think he's lying and that's just a cop-out used to retcon NS development others think he is telling the truth he is just incompetent and screwed up.
Again so much was put into it, if anything red herring would have been hinata in this situation. Or even if kushina did look like sakura and act like her, why say all that, why let minato say those things at the end, then why let your main character disobey/lie to his parents *dead parents…all for hinata…
I seriously don't think Kishi even knows what a "red herring" is. If something is developed, it's developed and no "red herring" can get rid of that development. It still happened. A red herring is supposed to mislead, yes, but not this way. It's supposed to mislead the characters and the plot, not just the readers. And intentionally putting in false parallels? That is LOW.
This^^^^….Red herring would have been a little something here or there, but the very foundation of the manga and its parralls and messages of shoot from NS.