It should be noted, in one way or another, that this isn't a United States case. This is taking place under Korean (specifically Seoul) law. I don't know the nitty-gritty details of how Korea handles copyright shit, but I'm guessing there are some differences between us and them.
It's mostly similar to the US copyright laws, including the Fair Use concept. Copyright Act in Korea was first drafted in 1957 to replace the Japanese one, amended twice (1986 with a new Constitution, and 2009) to better fit the international standards.
From what I've been reading, it was mostly for books (as widespread TV coverage wasn't a thing until the 80s) back then but it also covers "musical works, theatrical works, art works, pictorial works, motion pictures, and
computer programs, with the integrity of the author's works also taken into account.
I suck ass with Korean legalese but 김송기 v. 신사훈 (1993 June 8, case no. 93다3073) does seem like a precedence case for something like this. The Supreme Court ruled that a work under Copyright Act must be a creative expression of the author's thinking and feelings, not the idea itself.
I'm not a legal expert (especially copyright shit that happens in SK) but Epic Games can use this to say that Fortnite's creative expression of the battle royale (which is an idea) is 'cartoony' and 'casual' as opposed to PUBG's 'realistic' and 'hardcore' creative expression.
That being said, I do know slightly more about the political aspect of SK and knowing how conservative the Courts are (it's gotten significantly better since Park Geun-Hye's impeachment, however), another real possibility is that PUBG might win just because the devs are the Home Team.