https://docs.vmware.com/en/VMware-vSphere/7.0/vmware-vsphere-with-tanzu/GUID-EC79A6DE-477A-40C1-A90C-9DF96465CDA6.html

https://docs.vmware.com/en/VMware-Cloud-Foundation/5.0/vcf-admin/GUID-A56D8E59-A549-4624-BC61-4A92710F9FA1.html

A quote from reference [1] states that, "To add permissions to users or groups from vCenter Single Sign-On identity sources, the Tanzu Kubernetes cluster administrator can use either the vSphere Client or kubectl." Another quote from reference [1] states that, "By default, a Tanzu Kubernetes cluster includes a set of predefined roles that provides granular permission control for Kubernetes objects. The predefined roles enable cluster groups to be created with specific permissions across the Kubernetes namespace hierarchy. Administrators can also create custom roles to provide more granular permission control that is specific to their organization's requirements."

Explanation
According to How to Create a vSphere with Tanzu Namespace and Create and Configure a vSphere Namespace2, two of the steps required to create a vSphere with Tanzu namespace are:
* Define resource limits: You can specify CPU, memory, and storage limits for each namespace to control how much resources are available for the workloads running in that namespace.
* Use a DNS-compliant name: You must provide a unique name for each namespace that is compliant with DNS naming conventions.

Explanation
These are valid use cases for multiple clusters in a workload domain according to VMware documentation. A workload domain with multiple availability zones each containing clusters can provide high availability and disaster recovery by distributing workloads across different physical locations within a region. A workload domain with multiple clusters in one rack can provide scalability and flexibility by allowing different configurations and policies for different clusters within a single logical unit. Two clusters forming one stretched workload domain can provide resiliency and fault tolerance by synchronizing data across two sites within a region.