Thinking about it, was Kaido already been with Rocks or did he join after the event in punk hazard, because this going to lead multiple question.
If he join Rocks after Punk hazard, it would mean King was also a member of the crew. Yes Kaido plan to make his own crew, but what if Xebec beat him down and force him to join? Well that is one possiblity(with I don´t believe).
But if this is happening after the Rocks events, Kaido had his df already, with means and open up two new questions. Did Kaido get arrest already in God valley? I personal doubt it since Big mom probably saved him. But it seems like he later got defeated by a Navy officer and got put in Punk hazard as experiment? This means one of his 7loses are happend after his time with Rocks, either the Navy gang on him or Garp beat him back then. Hope we see and learn more about that during his flashback.