About the only way this works is if this is a second Ultra-Humanite, distinct from the Golden Age/JSA guy. I can see why one would want to reintroduce a new version of the character, as the old Ultra-Humanite was killed off in the "Stealing Thunder" trade of JSA.
(Yes, time travel [which is already being used in Booster Gold to have an Ultra-Humanite around]+death is cheap presents a lot of ways to bring back him, but I could see why you'd want a second Ultra-Humanite around.)