All true, which is why I specifically stated that the screenplay is 'book canon' (as it is written by JKR, the true source of 'book canon'). Anything added in the process of translating the screenplay into the movie is 'movie [semi-]canon' at best.
Oh, good grief, that's a silly and legalistic way of looking at it. A screenplay is just the instruction manual for creating a film, not a complete work in itself. It's kinda like the outline to a novel, a preliminary step in the process. Or rather, an intermediate step, since the script is preceded by an outline, but of course there's a whole additional stage involved (several, in fact) in creating a filmed work as opposed to a prose one.
Besides, surely Rowling was consulting with Yates, Kloves, and the rest of the film team from the beginning of the creative process, since she was creating these as films to begin with. And as a producer on the films -- not merely an executive producer, but a producer, which is a less honorary and more hands-on title in the feature industry -- she no doubt has a say in the decisions made in translating script into film. So you're positing a dividing line that doesn't exist. Both script and film are collaborations between Rowling and the others.
On the other hand, if you'd said which is canon, Emma Watson or Noma Dumezweni (and successors), I'd also have said 'neither' but clarified that Emma is closer to canon (especially if you accept book jacket illustrations are at least semi-canon).
Closer in what sense? Because she's white? She's also incredibly, sublimely beautiful, while book Hermione is much more plain-looking. So I'd say both actresses are equally far removed from the book character, just in different ways.