Increase capacity of disk of thick provisioned eager zeroed ends up with disk type thick provisioned lazy zeroed

Hi all,
I am trying to extend a disk with reconfigure_vm of type thick provisioned eager zeroed but afterwards the disk type is always changed to thick provisioned lazy zeroed. Please see code snipped below:

    spec = vim.vm.ConfigSpec()
    disk_devices = get_disk_devices(vm)
    vdevice_spec = vim.vm.device.VirtualDeviceSpec()
    disk_spec = disk_devices[0]
    disk_spec.capacityInKB = 100 * 1024 * 1024
    vdevice_spec.device = disk_spec
    vdevice_spec.operation = vim.vm.device.VirtualDeviceSpec.Operation.edit
    spec.deviceChange = [vdevice_spec]
    self.reconfigure_vm(vm, spec)

Remark: The get_disk_device gets all disk devices from the vm_object. Only the first one in the list gets extended.

Start with the reconfigure_vm call and the vim.vm.device.VirtualDeviceSpec edit shown in the issue, then inspect how get_disk_devices supplies the disk object. Reproduce the capacity increase for a thick provisioned eager-zeroed disk and determine why the resulting type becomes lazy-zeroed. Done means the disk capacity increases without changing its provisioning type.