He doesn't declare shit , Mihawk's Vivre Card confirms in name and actuality what he has as a strength title ; he's refered as what ppl say about him or what it's said about him :
といわれてる ( in the simple past ) = to iwa re teru = it is said that / they said that
So Law is just repeating what he hears around about Kaido , proving it's just a hear say and thus a Confirmation in Name and not actuality funnily enough even the Narrator did the same thing :
と呼ばれる = To Yoba reru = Known To be / called to be .....
Whilst when Mihawk's title gets mentioned :
<< 世界最強の 剣士としてこの額!!
『35億 9千万B』>>
<< As The World Strongest Swordman , He's worth 3.59 billion !! >>
Instead of using ( It's said that , they say = to iwa re teru / He's called to be , He's known to be = To Yoba reru .... ) , He used
として = To Shite in japanese As :
Funnily enough i should ask you this question , did anyone mention Kaido's title of WSC and confirms it without saying ( said , they say ) besides Law's panel which already put it as a reputation like what Zoro did ?
つて = Tsute = they say
Funnily enough Sengoku says it directly without the quote of << They say , it is said >> which shows which one is more credible
Like Mihawk :
Both titles were said by people , so there's a reputation and rumors around them but funnily enough we know Roger is the Pirate King because we saw him reaching laugh tale and even Marines confirmed that whilst they never did that with Kaido ; let's see :
PK Roger ? Check
WSS Mihawk ? Check
WSM Primebeard ? Check
WSM Sick Old Beard ? nah
WSC Kaido ? Nah
> Kaido is all about hearsay , while :
1/ Mihawk's title is confirmed in name and actuality and Marines mentioned it as something factual !
2/ Whitebeard's Title is confirmed in His Prime when he was in his prime , afterwards it's just the
reputation of his prime strength that lasted and the title got denied in Marine Ford because of Old Age and Sickness ( no one is sick to claim Kaido below Old Beard )
3/ Roger's Title got confirmed by Oden's Flashbacks also Marines mentioned it !
4/ Kaido's WSC is unconfirmed as every single one who has mentioned it added the hearsay quote ( it's said , they say , known as , called as .... ) and Marines mentioned him as the King of Beasts and his strength is hyped to be worthy of an Emperor level !
I cleared things out , because it's simple no one in his clear mind would make an argument for Kaido being the WSC because you have this fellow , Imu sama is a final villain who lasted 800 years , a creature who has achieved immortality as we have seen with Saturn ; so you want us to believe that Kaido is above IMU lmao ?
Drop the agenda and use ur brain a little bro , Kaido did good but don't overwank him to the edge !