The training contract would be very difficult, if not impossible, to enforce and I haven't heard of anyone leaving and paying the piper.
It is a recruiting tool to help them filter out the applicants "wasting their time." And for about 50% of the people who sign it, and can't afford to risk the money, it is a tool for new-hire retention. People will still come to recruiting events knowing the training contract is garbage and new-hires will still leave for a better paying airlines, because it is worth the extremely low risk. The pilot pay here is offensive. The management team from the executive level to the chief pilot's office may be genuinely delusional - they still seem to believe the pay here is justifiable, it's outrageous. People are looking past the growth and the "potential" of F9 and are leaving for something concrete. A bird in the hand is worth two in the bush.