I said from the start that Oda should have had Kaido defeat an Admiral. But it turns out Kaido was a legitimate bum trading blows with Shichibukai while his captain gets an unnamed Admiral lmfao.
If Rox beat an Admiral, it just goes to reinforce that Oda would only ever have the literal greatest pirate of all time be a worthy opponent for an Admiral. No subordinates like Primebeard, Mihawk, or Kaido could ever dream of this, and the chicken King and Garp had to team up on Rox after this happened.
This just reinforces the Admirals as by far the strongest in the verse, and all other Pirates are basically just silver medalists compared to Rox.