Black blades are markedly different from adding armament. Zoro adding Koka is the first step to making an actual black blade. Not that his swords actually became Black from koka
Mihawk said any blade can become a black blade in reference to his black blade. Same as Tenguyama saying Zoro can make enma black. In fact Tenguyama says making a blade black increases it's rank so Unless you believe Zoro increases his swords to supreme grade every time he adds Koka, then Tenguyama and Mihawk are talking about other things
In fact Zoro even alludes to this. When Gyukimaru starts talking about black blades, Zoro gets surprised and asks what Gyukimaru is talking about with the whole "Ryuma forged his sword black"
Why would Zoro who knows Koka be asking about how black blades are made if he knows about it already
What do you mean? Of course adding Koka to any kind of weapon ups it's quality. What's harder to break, Vergo's bamboo rod when it's just bamboo, or Vergo's bamboo rod when it's coated in Koka? Mihawk was explicitly talking about Koka in that scene in reference to the black blade, as the scene literally comes right after Zoro uses Koka for the first time.
Unless you think Oda for some inexplicable reason decided to drop some random scene about Black Blades out of the blue, completely out of context to the events that just transpired.
Best Sports Manga ever
Back when it was being published, Jump had its highest copies sold @SethTrollins if you want to read/watch sports genre then Slam Dunk, Haikyuu and Prince of Tennis are the best picks.
You can watch Inazuma too
Can't wait to see Pound and daughters reunion..., But I hope the cover story about Bege family would end as soon as possible. Because this cover story is boring most of the time. But I don't mind give Pound 2 chapters to see Lola's wedding.