And placing it in adapted screenplay also made no sense.
Actually, it makes perfect sense.... but only once you understand the byzantine rules that govern the various processes.
Different bodies have different standards, so the WGA or Golden Globes would have one standard for whether a screenplay is considered original or adapted, while the Academy has its own standard.
The Academy's standard has
always been more stringent; for example, they will move screenplays into the "adapted" category if the screenplay had a predecessor
even if it wasn't published previously (this happened to
Moonlight) or if there is a part of another work in the whole (
The Ballad of Buster Scruggs had a single tale that was either an homage, or an adptation, of a prior Jack London work).
In addition, if the movie is about a pre-existing character, it will be moved into the adapted screenplay category;
Borat 2 and
Before Midnight most famously, but even
Toy Story 3 fell into that categorization- which is very on-point.
In effect, because of the rules, it was always going to go into adapted screenplay in the Oscars ... no matter what you might have heard.
(Note- this doesn't mean that the rule is correct or incorrect, but it's not a new rule, and it wasn't deployed against the movie capriciously.)