Hello
This is correct, the volume's data will be as from the beginning of the conversion.
Cold cloning is not supported for a long time and the old Converter is not available for download either. Besides cold clone requires the machine to be shut down. You can shut down the SQL server only during conversion.
Alternatively you could eventually keep the volume size and use thin provisioning. This would work if the volume size is not bigger than the datastore size (only bigger than its free space) and the volume is not too fragmented, i.e. it is empty after a certain point.
Regards
Plamen