I mentioned one specific court case where one specific defendant was sued over one specific piece of content, where one specific plaintiff didn't move forward with the case after being presented with a defense, because they are serial plaintiffs that only want settlements. Your own source [2] says serial plaintiffs is what is happening! Not even sure where to start with you. The only point being about why there is not a decisive case on that particular defense because it never reached a judge.
More specifically, Liuxia Wong v Hard Drive Productions is a countercase, referring to Hard Drive Productions demanding a settlement from Liuxia for infringing on their copyright of a porn movie. Liuxia sued them back saying it wasn't copyrightable. What you will find online are motions to dismiss, which were denied. Then you'll find there was a settlement
https://casetext.com/case/liuxia-wong-v-hard-drive-prods-1
short discussion (about why its largely unsatisfactory in establishing any precedent and reinforces how there likely won't be any precendent on this matter as nobody is interested in taking it above trial courts): https://dietrolldie.wordpress.com/2012/06/05/case-closed-won...