AFAIK, a limitação ainda está presente. No entanto, pode ser visto aqui .
Volume ID name space restricted to AFS limits
E sobre a limitação de um caractere único: este link diz que
The maximum length is 22 characters, which can include any alphanumeric or punctuation character. By convention, periods separate the fields in a name. Do not apply the .backup or .readonly extension to a read/write volume name; they are reserved for the Volume Server to add to the read/write name when creating those backup and read-only volumes respectively.