Fair used to mean something that was pleasant or beautiful to behold.
Leave it the new-speakers to ruin that word too.
In this sense it once meant “the expectation of the estimator is equal to the value of the parameter” as the statisticians would say.
In less arcane terms, “the probability that you will be approved for housing is equal to your risk level.”
But that got contorted to “the renter will be given every benefit of the doubt.”