No, the problem was that airlines did not think they were allowed to examine the paperwork because ADA proponents told them it would violate the ADA to actually

No, the problem was that airlines did not think they were allowed to examine the paperwork because ADA proponents told them it would violate the ADA to actually verify claims related to emotional support animals. (And in CA, lower-level courts have actually ruled to that effect.) The importance of the new rule is twofold: first, it lets the airlines know that it does not violate the ADA to restrict emotional support animals, and second, it permits airlines to require verification that an animal is actually required for support reasons, emotional or otherwise.