From the output of the "Get-Help Update-NeSnapshotVolumeConvertReadOnly -Full" command:
Allows a repository candidate to be manually specified for use in the conversion. By default, the best candidate will be selected.
Accept pipeline input?
Accept wildcard characters?
It's not a required parameter for the cmdlet, so unless you want to manually specify a repository candidate, it isn't needed.
Thanks for the clarification - it looks like the "Get-NeRepositoriesConcat" cmdlet is designed to retrieve the list of repository volumes (sorry, I don't have an E-Series right in front of me to test). What data does that cmdlet return in your environment?