Yes you atleast require a standard edition license to perform these...
Great that it helped!
When I copied C.mdvk over to a new datastore the result was two files:
-rw------- 1 root root 322132001280 Jan 11 10:28 C-flat.vmdk
-rw------- 1 root root 466 Jan 11 10:28 C.vmdk
Who do I now have two files?
That's expected, and by design.
Virtual disks in ESXi consist of two files, a small header/descriptor .vmdk file, which contains metadata about the data file's disk name, size, geometry, etc., and the flat (in case of snapshots delta, or sesparse) .vmdk file, which contain user data.
It's the small descriptor .vmdk file, which is used in configuration (.vmx) files, and most commands that are available from the CLI.