Well first off, the relationships you make in the game are a personal skill. If you're voted out because of this challenge, it has nothing to do with the challenge itself, but it means that you didn't make the necessary social bonds to ensure your safety. That is a skill. That is Survivor.
Second off, everyone's scores are revealed. Meaning, if the members of the minority all lose consecutively ... but then you're the next one out, well, your position in the game doesn't seem to be so hot anymore. That is how Vecepia and Sean were able to flip people in Survivor: Marquesas and gain control of the game. Because of an "unfair" challenge.
Finally, your analogy to Mike isn't the same thing at all because we do not know if anyone would have flopped had the challenge taken place. Yes, he likely would have - but that's because he made himself into an immunity threat. Put Shirin in his place and her chances of staying alive grow stronger. But I know that you mean fundamentally the minorities have no chance of winning immunity... but this challenge is quite literally designed to show people where they stand in the game. It isn't my challenge, it's a basic idea that has been used in-show. Sorry, but if people in Survivor: Marquesas just refused to partake in the challenge because it was unfair, I don't think it would have gone well.
Also, like I said earlier, there is something I'm adding in the end that I don't want to spoil now - so please, bear with me.