VCF Operations 9.0.x
In VCF Operations 9.0.x, VKS Clusters are treated as persistent infrastructure objects. Automatic deletion from VCF Operations is not enabled by design on this version.
This behaviour will be changed in an upcoming release and VKS Cluster objects will move to a "Not existing" state and be automatically deleted from VCF Operations after being deleted from the vCenter.
Workaround:
After VKS Clusters have been removed from vCenter, they should also be removed from the VCF Operations.