I have seen you make the comment about "True name vs Other name". But the fact remains, that Oda, through Gorosei, has mentioned that is a Zoan.
Now, whether there is a case of "reliable narrator", that is a different issue. But, it is explicitly mentioned as Zoan. Now, Oda can do a Katakuri, and make it Zoan with Paramecia properties, just like Marco is practically a logia.
and others
I didn't say it's not Zoan.
Nor did I say he didn't add to the name.
But it's not a simple rename.
The GGF is still the GGF, but it also contains Zoan transformative properties.
I have good reason to understand that this fruit has multiple properties.
The clearest example of this is how the Paramecia Awakening works. Luffys transfers his ability outside his body which is the basis of Paramecia Awakening.
As to why a Zoan has Paramecia properties (or vice versa) I think we'll come to understand that when we understand more about Nika and about how DFs are created in the first place.
In my mind's eye, the simplest explanation is, Nika had GGF powers and a Zoan was made from his lineage factors.
But my ponderings aside, the GGF doesn't not exist anymore and Luffy isn't going to stop applying Gomu Gomu to attack names.
In short, don't make it a black/white issue. Because it's a Zoan doesn't mean it's also not a Paramecia. That defies our logic but then again, we know jack squat about DF production/history anyway.