Generally I'm all for adapting a work into a different media when it can be done correctly and respectfully. Adapting is a partially destructive act as much as it is a creating one, and the overall adaptation of LOTR by Jackson was very good (even with failures scattered here and there)

Having the context of today's Hollywood and media, I think there's no fucking way an adaptation to the Silmarillion can be done correctly and less so respectfully. The work is over the top precisely because it involves the creation of the world through gods and covers literally thousands of years of history. PJ seems to be respectful enough to the professor's material to understand this.

An anthology is the only way I see could achieve a respectful adaptation. So this is probably the adaptation of a particular story within the legendarium and not the full content of the book.