Yes, but in Real Life, this Vassals have had the Power, where this is not the case in CK3, because the AI does not know how to build a Holding correctly, they still build Military Buildings in Cities or Temples and build Economy Buildings in Castles.
Castles are for Levies and Men-at-Arms, Cities and Temples are for Money.
They also prefer to build more than 1 City or Temple in Counties, secondary Baronies, should be Castles, because it boost the Defence of the County massively, because Enemies have to siege down every Castle, before they can move on without losing Troops.
And this brings us, to the very terrible Military AI, which is now even incapable of using Men-at-Arms with Siege Progress, looking at you Ballistrai, they now prefer Levies or Siege Men-at-Arms to siege a Holding, ignoring any other Men-at-Arms with Siege Progress.
The AI in CK3, don't even push for Claims they have, even they have the Money and the Army to do so.