Eliezer's conception of fairness does not account for a whole category of "fairnesses". Let me put the devil's shoes.

There are many ways to divide the pie fairly. You may divide it according to the amount of people. In which case each person gets 1/Nth. But my way is more fair. You should divide it according to the weight of each individual, in which case Big Joe gets more than Tiny Anny.

Agile Carlos stands up and says: No, the fair way is according to metabolic rates.

It is naïve to say that the pie should be divided equally between persons, since the numerical level of personhood is not the factor that best correlates with what food is useful for.

To decide what should a pie be divided according to, we would start to play Reference Class tennis, because it is hard to decide if fairness should be symmetric on the person, the metabolic, or the size level.

So even though arguments will stop Zaire from taking the whole pie, I am still not nearly convinced that it is obvious that 1/Nth is fair.