In the
Haki page, Armament haki has Regeneration Negation. Iirc, the reasoning was due to Marco not healing from getting hit by Garp.
This could very easily be explained as simple Devil Fruit Ability negation.
Haki having Regeneration Negation can be so easily debunked by literally anybody healing from getting hit by Haki imbued attacks, such as Luffy
healing his tooth after fighting Sanji, who would need to use haki to harm Luffy.
I don't understand the mental gymnastic you would have to use to even come to that conclusion (Marco not healing due to Haki regen negation), when Haki was literally introduced in the series to negate Devil Fruit Abilites,