I see. Yeah I don't know how CC-BY-SA exactly works, but if that lawsuit gets through, then at least using content from the wiki in the movie should require the movie to be shared under the same license.
But then the next question is, what counts as content from the wiki? As an example, assume someone takes an idea for an SCP from 4chan and writes a wiki entry under CC-BY-SA about it. Then the text is surely their original work. But the idea of the SCP is not. So for just using the idea, if A24 could prove they got it from 4chan, then they could practically use it for free, because the risk that someone can prove that they are the author of the corresponding 4chan post is really low.
Anyways, I would hope some YouTube lawyer would look at this case and give their opinion. But maybe after the movie was published and we actually know what was copied.
Another anyways, I look forward to seeing the movie.