SAF pilots are bonded till they are 45 I think (correct me if I am wrong) then are allowed to join commercial airlines or else everyone would join SAF for a free trip to SIA. Pilot trainee dropouts stand a harder chance actually as it would mean a termination of contract by SAF if you don't make it through (happened to a couple of my friends before). It definitely does not look good being a dropout.
By the way, they do judge on aptitude and also by screening by several senior pilots. The past month, only 8% of applicants made it. Congrats to those going to OBS! Have fun!