I think this is probably the case. Same with WB and his WSM title, because with the gura he could destroy the world.
Kaido is WSC because of his devil fruit.
This Also explain the narration which we got when Kaido was introduced.
The WSC who can't captured and defeated few times but can't be killed... not even by himself.
And, thus people start considering that on one vs one bet on him because he can't be killed as he is the WSC