Understood but the article only provides a CLONE option not the COPY command.
That doesn't really matter, as long as the result is the same. Don't you agree?
For valid options run the man vmkfstools command.
vmkfstools -i source target -d disk_format -a adapter_type
The target disk_format depends on what you want/need, and the adapter_type is one that's supported by the guest OS. It's lsilogic for most OSs nowadays. However, you can check the current settings in e.g. the source .vmdk's descriptor file. If you omit these two options, the target format should be the same as the source.
André