I found a couple of interviews which might shed some light over this altogether...

First off, from Christopher Tolkien's interview from Le Monde:

Invited to meet Peter Jackson, the Tolkien family preferred not to. Why? "They eviscerated the book by making it an action movie for young people aged 15 to 25," Christopher says regretfully. "And it seems that The Hobbit will be the same kind of film."

This divorce has been systematically driven by the logic of Hollywood. "Tolkien has become a monster, devoured by his own popularity and absorbed into the absurdity of our time," Christopher Tolkien observes sadly. "The chasm between the beauty and seriousness of the work, and what it has become, has overwhelmed me. The commercialization has reduced the aesthetic and philosophical impact of the creation to nothing. There is only one solution for me: to turn my head away."
Also, Philippa Boyens' interview from Movieline:

By the end of the interview, she had us referring to Tolkien as Professor too, as she discussed the changes and adaptations she and her writing partners made to the text, the sad story of Balin the Dwarf, why fans should be very, very excited for 2043, when the copyright runs out on Tolkien's Middle-Earth compendium, The Silmarillion, and more.


Q: I have some good news for you. I looked, on the schedule. There's no movie coming out December 2043.

A: (Intense laughter)

Q: Don't pretend you don’t know where I'm going –

A: I'll be 80-something. I'll be 80 and somebody else will be doing it. That was really hard I have to say, that I couldn't go back there. [There are] extraordinary pieces of writing, extraordinary pieces of the puzzle in The Silmarillion. And we couldn't go near it. I haven't read it for 25 years. I just can't afford to have it in my head because we don't have any of the rights. And also it will just break my heart. I had to let it go.
My reaction? To be honest, relieved. I already have my own images of the book that I want to keep.

Hasn't read Silmarillion for 25 years and won't? That explains if some changes in the movies are wrong - how can you fully understand Tolkien's stories, if you don't understand Silmarillion? This makes Philippa as a questionable "Tolkien expert" in my eyes. And Jackson's interests are much more cinematic, those of a director I deem.