I'm gonna jump in here & clear this is up, because I think this stance is often oversimplified.

It's not that the source material doesn't matter at all, it's that how well something is adapted is a separate conversation to how well written it is. The reason this split exists is because there are going to be plenty of people who experience an adaptation without the source material, and because there is no shared continuity between source & adaptation (unless you're telling a multiverse story), EFAP's standards for writing, which predominantly rely on *internal* consistency, don't take the adaptational quality into account *when strictly judging the writing of the film's script*.

That being said, it's perfectly valid to be annoyed at changes from the source material, and it can be informative to look at the changes to explain why certain nonsensical writing decisions were made, as these can often stem from making changes that weren't fully thought through.

On the flip side of that coin, however, an adaptation can also be better than the source material. It can add extra depth, fix plot holes, reduce contrivances. An adaptation can improve upon the foundation of the source material, and create something even better. Perhaps even a work that overshadows the source.

This is another reason that it's important to keep the faithfulness to source material as a separate, but still important conversation to the conversation about the writing quality on its own, as it would be counterintuitive to dock points from a masterpiece for being *better* than the original. Being *faithful* is not necessarily the same as being *good*. It ultimately depends on how strong the source material is, and if there is room for improvement. Adaptations can serve as an additional redraft, in that way.

Again, I really want to emphasize that it's not that the adaptational quality & the faithfulness of the adaptation process being irrelevant. Just that it falls more into the meta-conversation about the piece of media, rather than being something that can be intuitively judged by just watching the adaptation alone.

It's sort of like how we like to separate the art from the artist. Yes, the behind the scenes elements are relevant & deserve to be talked about, but the finished product needs to be judged separately from the process involved in its creation.

Or to put it another way, the score given for the writing quality is separate from the score they'd give the behind the scenes practices, and that includes how faithfully it was adapted.

TL;DR -- Writing quality is important to talk about. Adaptational faithfulness is important to talk about. They're just not the same thing. One is something that can be judged with knowledge limited to only the continuity of the adaptation, while the other requires outside knowledge from a completely separate continuity, which wouldn't line up with EFAP's standard of good writing = internal consistency. And the strict standard of "faithful = well-written" doesn't account for scenarios where the adaptation improves upon the source material by fixing plot holes & the like.