In VMware Cloud Director (VCD), attempts to migrate or remove an existing storage policy may fail if vApp templates remain associated with that policy.
Even though the UI metrics may show no active usage, the storage policy is still considered in use because it is linked to templates in the content catalog.
VMware Cloud Director 10.x
The storage policy cannot be removed because it remains associated with existing vApp templates.
For more information on issues with removing Storage Policies from Organization VDCs, see the KB, Error: "Storage policy "############" cannot be deleted since it is currently in use." when detaching storage policy from Organization VDCs.