vmVnicNetworkResourcePoolKey property cannot be set to -1

def add_dvPort_group(si, dv_switch, pg_name, pg_vlan_id):
    dv_pg_spec = vim.dvs.DistributedVirtualPortgroup.ConfigSpec()
    dv_pg_spec.configVersion = '0'
    dv_pg_spec.name = pg_name
    dv_pg_spec.numPorts = 8
    dv_pg_spec.type = vim.dvs.DistributedVirtualPortgroup.PortgroupType.earlyBinding
    dv_pg_spec.vmVnicNetworkResourcePoolKey = '-1'
    dv_pg_spec.defaultPortConfig = vim.dvs.VmwareDistributedVirtualSwitch.VmwarePortConfigPolicy()
    dv_pg_spec.defaultPortConfig.securityPolicy = vim.dvs.VmwareDistributedVirtualSwitch.SecurityPolicy()
    dv_pg_spec.defaultPortConfig.vlan = vim.dvs.VmwareDistributedVirtualSwitch.VlanIdSpec()
    dv_pg_spec.defaultPortConfig.vlan.vlanId = pg_vlan_id
    dv_pg_spec.defaultPortConfig.securityPolicy.allowPromiscuous = vim.BoolPolicy(value=False)
    dv_pg_spec.defaultPortConfig.securityPolicy.forgedTransmits = vim.BoolPolicy(value=False)
    dv_pg_spec.defaultPortConfig.vlan.inherited = False
    dv_pg_spec.defaultPortConfig.securityPolicy.inherited = True
    dv_pg_spec.defaultPortConfig.securityPolicy.allowPromiscuous = vim.BoolPolicy(inherited=True)
    dv_pg_spec.defaultPortConfig.securityPolicy.macChanges = vim.BoolPolicy(inherited=True)
    dv_pg_spec.defaultPortConfig.securityPolicy.forgedTransmits = vim.BoolPolicy(inherited=True)
    task = dv_switch.AddDVPortgroup_Task([dv_pg_spec])
    wait_for_task(task, si)

Running this code the vmVnicNetworkResourcePoolKey property is not set in the vCenter and the config version is set to 1 instead of 0

Start with the reproduced add_dvPort_group example and the vim.dvs.DistributedVirtualPortgroup.ConfigSpec fields, especially vmVnicNetworkResourcePoolKey and configVersion. Run the AddDVPortgroup_Task flow against vCenter and compare the requested values with the resulting configuration; done means the reported behavior is explained or corrected.