I think it's great that The Giant is very similar to the original releases as it would be a great compliment to the largely convoluted Shadows of Evil map. I've heard that the new map will be gigantic, have new bosses and enemies, etcetera, so I think they didn't change The Giant much (from what we've seen so far) so fans can have access to a more classic zombies experience, similar to how Nuketown zombies did not have much depth to it compared to Green Run upon release.
Maybe the Giant acts as a break from all the innovations the newer map has to offer... Even if it is the same map for a third time.