"Unfair" means there is a different assumption, context or a rule applied to different people. For example, lets assume there is a competition where each team is required to use only one computer. Therefore in here the context on every team is to use one computer. Now if there is a team using multiple computers above this context, they will be having a different context. This is a truly unfair situation.

Now to this situation. Everyone is competing under the same context that there are system tests, and if their code is close to the TL, they will get a FST if they are unlucky. There is no "bias" to this "luck". Can we really call this "unfair"? As a metaphor, let's think of a ladder-and-snake board game. Do we call this game "unfair"? Not really. This is due to the fact that everyone participates under the same assumption that there is some luck factor deciding the winner, and everyone's expected probability of winning is equal. We can apply this to our situation as well, and get the conclusion that, this is not really unfair, just that there's some luck factor deciding the results.