He used retcon in the right form here. Katakuri was initially a logia, where Oda wrote it out like that in the weekly shonen jump release of the chapter but the volume released changed that and Oda turned it into a “Special Paramecia”
Retcon isn't when you fix a chapter or page, it's when later, you ignore a previous statement or reveal or fact from previous chapter & completely introduce a new one that contradicts that old one, so the two contradictory ideas would still exist at same time in the story.
But when you change something from jump release to volume release, that's just fixing
"revise (an aspect of a fictional work) retrospectively, typically by introducing a piece of new information that imposes a different interpretation on previously described events."
As i said, introducing "New" piece of Information that is different than previously described one. Not completely "Replace"
And i replied not because of the decision, i just wanted to explain that there is no such Sub-Type called "Special Paramecia"
Kata's DF is just a Paramecia, it's just that Jinbe called it "Special", similar to how Robin called Enel's DF "Invincible"
They are simply very remarkable DFs