There was a new ruling just a few days ago on the same issue. Don't know what level. But this clause will never make it to the federal level. Anytime you try to take fedex to court for contract violations, it isn't a federal case, and fedex will try to force arbitration and ask the judge to throw your case out because of the arbitration clause. Then you'd need to challenge the validity of the arbitration clause- a whole 'nother additional cost before you can go to court. You can read the ruling to see why the clause is so unfair. But the fact that the clause has already been found unenforceable in several venues makes it easier and cheaper to fight it.
Claiming employee status is outside the scope of the arbitration clause, and in that case, it isn't even necessary to challenge it. Only if you are suing for damages as a contractor would the arbitration clause apply. But it is a perfect example of how one-sided the contract is.