At this point u have to be a idiot to take this vivre cards infos as a unchangeable truth.
Of course when something will have more parts in the story Oda won't just let they put this on a money making side product, it will be in the Manga.
Sengoku CoC is in the Vivre Card because he isnt important to the Story and don't have much a role anymore.
But, of course characters like Zoro, Mihawk, Garp and Dragon have CoC, and as they have more parts in the main plot , Oda will show it in the Story.
Zoro especially has showed CoC some times since Wano, but most likely Oda is saving the official in-world confirmation for when he and Mihawk clash and Mihawk give some info on how CoC is the key to turn the a blade black.