Good question, but I'm not sure they have a bigger concern, think they're pretty much hand-in-hand at the moment. "Proving" you got it at Disney may be hard to do, but that won't stop the lawsuits from being filed and costing Disney millions of dollars to defend against. I completely agree with protecting the workers, and in this case I'm glad there are unions that can provide one or two fronts for Disney corporate to deal with in lieu of thousands of individual workers, but unions also have an eye for looking out for themselves and their pocketbook so not everything they do is for altruistic reasons; most unions would not blink an eye if they could bankrupt management...until they realize that means no more union dues coming in. No, not particularly anti- or pro-union myself as I have worked while in a union and without a union in some of my positions, and know both have their positives and negatives.
And no, not a lawyer, but quite a few friends are...and most of them learn how to break a generic "come and you assume the risk" clause in any contract by the end of their first year of grad school. All you would have to do is go into a room and find a spec of dust in a covered, hidden corner of the room behind a dresser against the wall and Disney can be shown that they aren't keeping up their end of the contract in providing a "safe environment." How many lawsuits were filed after 9/11 against the building's owner even though every tenants' contract with the owner had a waiver of liability risk clause in it? Same thing here...Disney has to highlight that language (though similar language has been in their agreements for years) as a starting point, but they know it's not going to stop a majority of the lawsuits.