jrmyl is 100% correct. It is a fair process and you need to play the game by their rules. It is not all about flying only.
Last 2 years about 50% have failed the evaluation, but only 1 of them was a surprise to me, all the rest were predictable.
I suspect the same will continue for a while, many of our recent new hires do not have the experience or maturity to be a Captain in 3 years, and some lack the right attitude and work ethics.