They didnt fight in this chapter.
Sure, Mihawk can pierce him, that was never the question.
Kaido is WSC, there is no doubt about it. Nobody has even close to his stats.
As I said, cheap shots dont change anything about his power level.
Kaido is not the WSC, it is now impossible for him to be the WSC. He may have physical strength incomparable to other sentient beings (I doubt he can put out the same strength as Zunisha though) but that only means he can beat anyone in an Arm-Wrestling contest. Nothing more.
There are people stronger than Kaido in overall strength. That much is clear. 1 one 1, Kaido CAN lose to many people. And frankly, he didn't win against BM or Shanks, the only two time in the manga when he fought Top tiers.
Another thing: Stop associating Zoro's power-level with Kaido's. Kaido "downplaying" has no effect on Zoro's power-level at EoS. Only Mihawk's power-level has an effect on Zoro's power-level at EoS.