Like how do we even know that blades need to get used to haki pools, isn't that just head canon? To me, it looks more like the skill is about releasing enough to satisfy Enma, who needs a lot, but also not releasing so much that you die. But automatically, because Enma requires so much Haki in the first place, attacks with it will be stronger. Does that make sense?
Here is Oden as a child
How can Oden as a child wield Enma, at the same state Adult Oden was wielding it, naturally Emma's thirst grew and that's why no one's been able to match Oden until Luffy and Zoro come to Wano.