The standard argument in response to such comments is that at the end of the day, the Potterverse is fictional and J.K. Rowling can do whatever she wants with it. Having said that, audiences today are very wary of narratives that are not cohesive. And yet, such disparities have had no effect on the popularity of the Potterverse today.
Why is that?
By nature of creating a series and not a single Harry Potter book, Rowling created a comprehensive universe that audiences could truly lose themselves in. She created interesting storylines for all her characters which audiences could explore at leisure. With pottermore.com , audiences could further immerse themselves in her world, and actually feel a sense of belonging (I got sorted into Ravenclaw, by the way).
All of this strengthened the thought leadership of the Potterverse in audiences’ minds. Once they were invested in that world as a whole, Rowling could do as she pleased without fear of diminishing the Potterverse’s popularity. So now, no matter what other people say, Potter fans will still faithfully consume every new product that Rowling creates (myself included).
What’s interesting is that every large-scale successful brand today has done exactly what Rowling did – they created a universe that audiences chose to invest in. Take Apple, for example – no matter how many logical flaws are pointed out about their phones, people will still line up to buy the latest release. No matter what content they create, their aspirational perception in audience’s minds remains as strong as ever. And tomorrow, if a better phone hits the market, chances are people will still buy an iPhone because they want to belong to the Apple community.