Zoro hasn‘t done that since the fight with Cabaji way back in the beginning of One Piece.
There’s a big difference between being knocked out, and just lying down and deciding you’ve done enough and can’t fight anymore. If Zoro’s in Kid and Law’s position, he‘s at least trying to fight off the fodder around him.
With things like fighting on after Hakai/taking Luffy’s pain/Luffy‘s ID Marineford gauntlet Luffy and Zoro have shown the capacity they have to push their bodies above and beyond what is normal even among their general level.
Other characters do not get the benefit of the doubt in this area with people saying “oh, if Zoro or Luffy can do it character X can do it.” Because what Luffy and Zoro show in these moments is the insane drive that show why they will achieve their aims of getting to the top, why people like Shanks and Mihawk were impressed by them when they were little more than fodder in the grand scheme of things. It‘s not even feats, it’s an extraordinary personality. Kid and Law don’t have it. It’s possibly why they don’t have ACoC either- because Haki is called what it is for a reason, ambition, willpower, drive etc.
Kid and Law are certainly strong and all that, no denying that, but this is an area where they are, to try and quantify it, an A and Luffy and Zoro are an S. They have to show the feats, they don’t get a bye.
It’s like Whitebeard’s last stand at Marineford. There are other top tiers, but there‘s little reason to believe that all of them could match what he did there, if their bodies were basically collapsing under them before the fighting even started.