That Unreal 4 job listing is older than the leak - so it's entirely possible whoever wrote that leak saw that it was a tidbit no one noticed and wrote it up.
But yeah, unless that role is for a dedicated UE4 VASG-role, then San Diego's new project might be running on Unreal 4 instead of any existing WWS in-house engine.
I don't know why WWS don't share engines much more often.
This isn't the same situation as EA's frostbite where the engine had to be converted from 1st person to 3rd person. We already have a great engine that was made specifically for Uncharted dammit!