The official chapter referenced to their Stamina. He was already significantly damaged hence he decided to use his best attack.
Also the manga has already shown us how Zoro should look if he run out of haki. That wasnt shown after Asura.
So like I said, it is unsubstantiated and quite false
> The official chapter referenced to their Stamina
The raw didn't mention if it was his stamina or his haki, it depends on how you read it. And about translations, I don't remember what the english translation said but even if it's stamina, the spanish translation I remember they said energy, which again, it depends on how you read it since the japanese chapter didn't say what is he wasting.
> Also the manga has already shown us how Zoro should look if he run out of haki.
This was shown when Zoro didn't have any control with Enma, which basically Enma draw more Haki than what Zoro needed/wanted, that's why his arm looked like that for a moment.
From my PoV Haki is like a water bottle. When there is no more water to drink and you keep sucking, the bottle deforms because you are sucking the air within the bottle, that's what in my opinion happened with Zoro's arm when he used Enma for the first time. First Enma sucked the haki and even when there was no more haki, it kept sucking until it leaved his arm like this.
But again, this is just my opinion.
> That wasnt shown after Asura.
Once he used Ashura, Zoro couldn't stand up anymore, of course this could be because of the wounds he received which weren't normal, but anyways, he tried to stand up and he couldn't the panel was very similar to when Luffy was trying to stand up once he lost the Gear 4th in Dressrosa.
The official translation doesn't indicate anything about Haki though, and it's not Zoro speaking for himself but in general
The official translation couldn't translate anything about haki because the same raw doesn't mention what is it what he is wasting. And about the second part, hmm i guess it could be taken as he was talking in general but since he was talking about his own limit, i'm pretty sure it's okay with taking that sentence as if he was talking about himself.