Now is where things get interesting
She asked him out just because the score was high, so what if someone fakes a score?
Of course, once the idea becomes popularized, people may check the scores from their end to verify, but initially, who would consider the possibility?
Then it gets spicier - people will start to develop an opinion on whether the app is bullshit or not when people begin using these arbitrary scores to determine whether they should date, especially those who break up with people they had a high compatibility score with.
I can imagine the story might go in a direction where MC dates her, they break up for some particular reason, maybe a secret on either of their ends that's a dealbreaker. Then MC realizes the app doesn't mean jack shit, but who else will believe him? By then there would probably be plenty of success stories with happy couples due to the app and everyone would be using it.
This is before we even consider the idea of sabotaging scores and analysis by baiting controversial discussions on social media, or even paying off the developers to change a score.