The point is, there's no reason why the specialty shouldn't get a Catfall-esque ability; if you're the type to go for the arteries and tendons than the reduction of falling damage will be excellent for when the giant punts you into the air and causes you to fly a good couple of yards up and over. If you're the sort that starts climbing all over a dragon while it's in mid-flight, then it's beneficial for if/when you get bucked-off.
Is it more useful to a Giant Slayer than an infiltrator? An acrobat? I'm not saying it couldn't be useful, but Specialty design, ideally, isn't "throw in everything useful." I don't being purposefully punted by a giant something that happens very often, and when you are clinging to a dragon, my thought is that you really wouldn't want to fall off. Like, at all. It seems like a very specialized area not very closely related to slaying things that are big. Right off the cuff, a Dodge bonus seems more relevant and desirable.