Disney isn't going to sue anyone for leaked photos. Universal has and will sue people for leaked photos. That is really the difference here. Noticed that the Uni leaked photos got taken down long before most people saw them where the Disney leaked photos are still up. Universal contacts the source and gets them pulled down before they spread. Disney has bigger fish to fry like why all their rides are delayed and how to get people to NOT realize they have no new rides.
Also, I think Disney feels any kind of press is good press and Universal holds their cards closer to their chest and THEY want to be in control of all media out there for them.
It's about the principle of the point. You can't act furious over Kong leaks and then go willy nilly with these. Regardless they are leaked photos of unfinished show pieces that Disney didn't release themselves. Just because Universal acts upon it while Disney doesn't does not make it right.