Creating seSparseFormat linked clones?

Have anyone tried creating seSparseFormat linked clones using vCO 5.1?

I followed instructions in William Lam's blog at virtuallyGhetto: Creating SE Sparse Linked Clones Using the vSphere 5.1 API but when I execute my workflow vCenter Server is responding "The specified delta disk format 'seSparseFormat' is not supported."

Source VM does not have seSparseFormat VMDK, it is with normal virtual hardware v9 thin disk with active snapshot, although VM does have cbrc digest enabled.

Here is quick and dirty code I am testing with at the moment.

var disk = new VcVirtualMachineRelocateSpecDiskLocator();

disk.datastore = datastore;

disk.diskId = 2000;

disk.diskMoveType = "createNewChildDiskBacking";

disk.diskBackingInfo = new VcVirtualDiskFlatVer2BackingInfo();

disk.diskBackingInfo.fileName = "[" + datastore.name + "]" + vmName + "/" + vmName + ".vmdk";

disk.diskBackingInfo.diskMode  = "persistent";

disk.diskBackingInfo.deltaDiskFormat = "seSparseFormat";

var diskLocator = new Array();

diskLocator.push(disk);

relocateSpec = System.getModule("com.vmware.library.vc.vm.spec").getRelocateSpec(datastore, diskLocator, host, resourcePool, transform);

Have I missed something or has seSparseFormat been disabled in vCenter Server 5.1 update 1 API?