>>3110863Seems to be mostly related to how they changed how her character works in the Rebuild movies.
In the original series, she's cloned, but she seems to retain some of her knowledge/personality between her clones. Her mind (or part of it) is either separate from her cloned bodies or somehow transferred in-between them.
But Rei Q seems to not have any of Rei's prior knowledge and personality developments. She seems pretty damn blank. She might be a return to a much earlier state. Or they might have created her different and/or based on different things. Or who knows.
Rei's "soul" apparently escaped somewhere during the second movie. In the third movie, they created Rei Q mostly as a lure for Shinji it seems. She was even more neglected as she developed so she really seems blank. But you can still recognize Rei's temperament. And she seems upset by the idea that she's not really Rei.
So I understand why they say that Rei Q isn't Rei, but the butthurt is pretty autistic desu. To me it's just a "fork" of Rei. A very sad one. But from Rei's perspective maybe it's not any worse than the others.