Nobody knew King powers back then but he was quite likely to be Zoro fight and as Zoro fight he was sure to be a pain for him and at least an high diff fight.
So no saying that Zoro would walk over King was always crazy even day 1
That's exactly why it made sense to say what they said back then. We don't know how strong King is, so our best bet was thinking he was comparable to Katakuri but King turned out to be a freak even among the YC1s.
Most people didn't see Zoro going back to King during rooftop. Even I was rooting for Sanji vs King with Chrono. After Hakai, many expected Zoro to fight King with broken bones. And Zoro also hasn't gone all out to beat his opponents since the beginning of the TS. So they weren't wrong in saying what they said given the information we have back then. They aren't so inaccurate even now as Zoro is clearly not using the same level of attacks that he was using atop the roof.
Even now, Katakuri or anyone relative to him, except Marco and Jozu, isn't withstanding a direct hit from Flying Dragon Blaze.