UTR, the problem is that you can't make the airline industry one in which once you get past the selection process you can't be failed. The C&T department must have the ability to freely fail pilots if it is warranted. The fact that the guy got through his endorsement but struggled on the line is no great surprise, flying the line has a different set of challenges to just doing emergency drills and approaches in a simulator. It seems that he can fly the aeroplane in a controlled environment but for whatever reasons he struggled in the real world.
I don't disagree that Jetstar may have been unfair to him, but I think trying to get out of paying for the endorsement is taking the wrong approach.