The WoL is actually the villain that set the whole story of FFXIV in motion. They came up with the concept for the Hero in the days of Amaurot, but the idea for a hero requires an opposing force or threat to stop. Given this, the other members of the Convocation rejected the idea, causing the ancient form of the WoL to unwittingly bring about the end of the world with their secret creation lab, a "Devil's Lab," if you will, hidden in the underground.
Only, the creations the WoL brought about wrested free from his control, gaining souls without consent, and they were far too powerful for his "heroic" self to stop. Events snowballed into the calamity. In the present, we play the WoL with amnesia of their past self. Now we get to fulfill the concept of a Hero, through and through.
We didn't join up with the Hydaelyn creators because we believed ourselves only capable of making monsters. Plus, we had to contend with our misbegotten creations still left from the Devil's Lab, which were now tied to Zodiark, because we tied them to the planet itself in the form of elemental avatars. Being tied to Zodiark meant that he would not erase them.
So when we make the Primals in Eden, the reason they come out looking completely different is because we're actually unwittingly drawing on our first memories of them, when we made them through the lab in the past. This is why Titan has an ATV.
The only exception being Shiva, but this is only a silly thing I cooked up as an excuse for the game to reference the Magitek Research Facility... and more importantly remix Devil's Lab. God, I would kill for that. And yeah, I know, Castrum Abania references both the Magitek Research Facility and Mako Reactors pods within its dungeon design, but I want big glass tubes with Phantom Beasts floating in transparent goo, dang it!