Well hang on..... Oden told Kaido to
get stronger ...... Maybe Kaido developed his hybrid form after the Oden Fight. We dont know how these Ancient/Mythical zoan fruits work yet. Especially the Mythical, they could have very special circumstances for their fruit.
If you think Kaido attained hybrid form after Oden's death then it also goes in line with what i initially said, the WG are facing a harder challenge than Oden. But he didn't, we already know how ancient hybrid Zoan works and mythical Zoans being different is still speculation.
From 1004 and onwards with any damage Zoro inflicts on hybrid Kaido, EoW Zoro > Oden gains more merit.
It was always obvious Kaido had an hybrid form. Kaku could go hybrid shortly after consuming the fruit. And Kaido had the fruit for around 18years to the confrontation with Oden, so more than enough time to have hybrid.
The implication of the Kaido vs Oden battle then was never about straight feat battle estimation, but portrayal, which was the hybrid wielding Kaido refusing a direct confrontation with Oden, coming fully prepared and out numbering Oden's group while having a spy in his group and still admitting he should have died that moment, with the recent chapters still putting Oden as one of the people who could fight / beat him.
It was obvious, but what he showed in base from chapter 994 to 1001 was what i initially thought to be what he can do in hybrid. The increasing gap between his mythical forms changed my mind.
It's starting to look like a plot driven moment. Kaido fully understood what Oden is capable of, he fought him more than once, considered him among the few who he shouldn't fuck around with and prepared everything for the encounter yet when the fight started he remained in his weakest form spamming attacks that Luffy shrugged off, which greatly increased Oden's chances to pull off a win in two shots.