The first time the 10 Titan Captains of the Blackbeard Pirates were mentioned was during Dressrosa by the colosseum announcer.
Doflamingo just few days back in Punk Hazard was questioning Aokiji about his status and about how he’s heard rumors about Aokiji.
Same with G-5 Marines. They were shocked from Aokiji just having connections to the Underworld. Why would they be shocked at that if he’s supposedly with a Yonko?
So unless a colosseum announcer somehow knew more than Doflamingo and G-5 Marines that means Aokiji was not with Blackbeard at that time, or at least not publicly known as one of his captains, since all 10 Titanic Captains are famous according to the announcer. And Smoker wouldn’t have to ask such a stupid question if Aokiji was with a Yonko.
Then in Chapter 1064 we see Kuzan dressed as a pirate and being confirmed as part of Blackbeard’s crew.
Notice that Kuzan was not dressed as a pirate back in Punk Hazard. He was still in his casual outfit.
He was in his casual outfit post Dressrosa (an arc where it was revealed that Blackbeard has 10 Titanic Captains) as well reacting to Luffy’s bounty.
This pretty much once again indicates that Kuzan was not part of the crew even post Dressrosa.
And then we have Road to Laugh Tale chapters, which were post Wano raid, where the 10th Titanic Captain was still hidden:
The 10th Titanic Captain of the Blackbeard Pirates may still be a new character.