I have to agree. I thought the character of Cyborg was better developed in the Snyder Cut, but Fisher remained the least compelling character in the story when he could have really stood out - and carried more weight in the story. He wasn't at parity with Flash and Aquaman, the other new characters introduced in Justice League, even though his backstory had a more central connection to the plot than either of the other two newbies.
However, you're right in that it has nothing to do with why he would make up these accusations. He certainly doesn't get anything from it.
At the same time, Whedon could honestly see it differently. People misinterpret events in their memories all the time - exaggerating the reality to fit their perception of it. Especially in such an ego-driven profession as the movies, acting and directing.
Personally, after watching the theatrical release of JL, I remember thinking that Cyborg was the character I wanted to see more of and enjoyed his interactions the best. Especially his scene with Diana made me want more from him.