Low key I think this is actually what happened lol.
In Kaido’s “top 5”, Roger and WB were placed on a higher elevation than the other 3. I think this is because they each gave him 2 of his 7 L’s, while the other 3 gave him only 1 of his 7 L’s. We saw Oden give Kaido an L on screen, so that accounts for 1 of the 7. WB obviously beat Kaido in the past given Kaido’sc obsession with fighting WB and the fact that we know Rocks crewmates were always at each other’s throats. WB probably gave Kaido an L when Kaido was recruited into Rocks, and another L when Rocks disbanded. Roger also probably gave Kaido an L before God Valley, and another L at or after God Valley (Roger was top dog after God Valley, so obviously the battle hungry Kaido would seek to challenge him). Kaido is obviously the type of guy who wouldn’t follow a captain weaker than him, so he almost certainly challenged Xebec and lost. That’s 6 out of 7 L’s accounted for. It makes sense that the last L of his was given by the 5th guy (Shanks) in his top 5 vision.
It’s unlikely that Shanks and Kaido had a convential fight, with Shanks sending Kaido bruised and battered back to Wano. Shanks showed up to MF totally unscathed, so I doubt that that had a convential fight. I don’t think Oda would wank Shanks that much. However, it’s very probable that they had a CoC stand-off to determine who would get their way, with Shanks obviously coming out on top. Kaido values Haki very highly, so it makes sense that he would consider Shanks displaying (vastly) superior Haki to be a defeat