that's why it isn't a fuck up, just because he "upgraded" his technique doesn't mean he wouldn't use the previous one anymore….
not to mention that by the time that chapter came out that episode was most likely already done, that and if they would have had the "upgraded" one it could have counted as a spoiler here...
you're ignoring the main point, he didn't name his attack in the manga.
They not only ignored that fact but they also changed that simple attack for one zoro doesn't have any reason to use. Everyone of that attacks zoro has shown since the timepskip were new ones or upgraded versions of the old ones. I'm sure we won't see any of his old techniques ever again, but that's not what really matters.
What matters is zoro used an unnamed technique and that's a fact.