With recent developments in the story and the theorizing that has stemmed from this, I’ve noticed a surprising amount of people who aren’t aware of this fact. Zoan type devil fruits have a unique property known as “models.” The general gist of it is that you can have the same general type of animal: for example, let’s take our favorite Reindeer, Chopper.
Chopper ate the Human-Human fruit. Now, normally, that would mean that nobody else could have the same type of Devil Fruit, and technically, that’s still true. However, we have Sengoku. Now, you may assume that he ate the Buddha-Buddha fruit, but that isn’t actually true. Sengoku ate the Human-Human fruit, Model: Buddha. Meaning that there are actually multiple Human-Human fruits, sort of.
Now you may say, “OK, but that’s a regular zoan and a mythic zoan, that’s pretty different.” So let’s look at Boa Sandersonia and Boa Marigold.
Both of them ate different models of the Snake-Snake fruit: Sandersonia ate the Anaconda model, whereas Marigold has the King Cobra model. And some of these categories are pretty broad. For example, let’s look at the devil fruits of Kaku and Dalton. Now, you might think that they ate the Giraffe and Bison fruits, but in reality, they both ate variations of the Cow-Cow fruits: the Giraffe model and Bison models, respectively.
To sum up my point, there’s a pretty wide net to cast with Zoan type fruits. So if you see a theory saying that so-and-so character has a Bull devil fruit, and go, “No, that’s not possible, Dalton has that fruit already,” it’s actually entirely possible that so-and-so has that same fruit as well, in a different model.
*Theory by mcallisterco