I never said swords have Haki.
You didn't answer my question is why Zoro said Enma's power if this is just zoro's own ryou ?
Zoro is controlling his ryou so he should have said I need to release more of my Ryou.
Therefore Enma's power isn't to drain Ryou, Enma use ryou for his power.
Its a graded blade soo it is a powerfull sword with potential to become much stronger that Shusui.
Its CURSE is to cut more than it needs to, soo mastering it improves your haki controll a great deal, all that pannel says is that Zoro was not slashing with all his might since he was holding enma back as to not drain his haki needlessly. What he means is that he should allow enma to draw more of it soo his slash will be stronger.
Its like driving a realy fast sportscar that has poor brakes, sure it can go from 1 to 150km/h pretty fast, but its pretty damn hard to stop, soo thats why Zoro limited its speed, but in this case, crashing the car=fainting due to lack of haki.