All Yonko, every single one of them, are at best silver medalist who sat on their ass all day for most of their career.
This is true of Kaido, Big Mom, Shanks, even Whitebeard. You can think of Akainu what you want, I personally think he is scum of the highest degree, but he was SPITTING when he shit talked Whitebeard (and by proxy other Yonko) at the end of Marineford.
Xebec is not part of the Yonko Agenda just because 3 Yonko were on his ship and one is his son. So even if he no-diffs an Admirals and that contradicts the whole "they would never be disrespected by Oda like the Yonko" idea for the Admiral agenda would agree it does nothing for the Yonko Agenda.