I have found the issue : BUG with case sensitivity issue
Replace "NONE" to "none" for parameter "NTAP_VOL_CLONE_RESERVE" required for VMFS datastores to be cloned to perform host based VMDK copy / restore.
########################################################################################################################
# Clone Options #
########################################################################################################################
NTAP_VOL_CLONE_RESERVE=none
Note that every time the GUI is use to perform the restore, config file reverts back to using capital letters.
We either use CLI (post editing the config file to using lower case - "none") or override GUI option as below -