Was it contradicted? I honestly never heard that it was. What are the statements that contradicted it? And what feats does she have that are superior to Superman to back it up? Over the years there have also been several direct comparisons in fights that back Supes over her, such as his better performance against H'el. Which was him at half strength apparently, due to recent revelations. Also, wasn't one of the points during that arc that she is new to her powers and didn't really know how to hold back well at that point yet? I mean, I could be wrong.
Also, why not use the k-nite ring? Just because Batman took it out doesn't mean he didn't believe the theory. That is kinda reaching. More likely he just wanted to end it fast and avoid more fighting.