Well you basically just added to my point. Zoro having higher reserves of Haki wouldn't mean he's more skilled at using it. Being able to control it to the point where you can cut things that others can't is what your skill level is. There is a reason why Zoro wants to learn how to cut fire, and not because it's just something that would be cool to do.
Prior to Luffy learning External/Penetration Haki, Hyou was more skilled than him at it. But I guarantee you that the strength and reserves of Luffy's Haki >>>>>>> Hyou.
Idk about Luffy's Haki reserves >>>> Hyou's, Katakuri has shown greater raw Haki level than Luffy, even likes of Cracker has and I doubt a trained special swordsman to whom Haki is one of the most important aspects of his training hasn't bloomed his Haki reserves to a level higher than a new world rookie. I doubt if Hyogoro used his CoA guard, Hody would be able to bite through him, that's not Haki control as Luffy was able to coat part of his body that needed to be coated, but strength of his Haki just wasn't enough.
But I agree with your overall point Haki reserves doesn't mean Haki control. But its also the fact that Zoro after his training has been able to attain his Haki control to the level that he can prevent Enma from going overboard with Haki sucking on will.
Kinnemon has ability to cut fire but then again that could just be elemental swordsmanship which has nothing to do with Ryou. But maybe Kinnemon has better control idk, we need more data on how fire cutting abilities work.
With that said, I don't necessarily think its an insult for Zoro to have less of a Haki control than Kinnemon, he is one of the most skilled Haki users in the world I would say even if his Haki reserves are average at best.