[OpenAFS] "group prefix doesn't match owner"

[Adam Megacz]

Is there any reason why pts won't let system:administrator create groups
whose prefix does not match any user?

  $pts ex blah
  pts: User or group doesn't exist so couldn't look up id for blah
  $pts creategroup blah:booh
  pts: Badly formed name (group prefix doesn't match owner?) ; unable to create group blah:booh 

Clearly this can be circumvented by system:administrator:

  $pts cu blah
  User blah has id 100015
  $pts creategroup blah:booh -owner blah
  group blah:booh has id -1012
  $pts delete blah
  $pts ex blah:booh
  Name: blah:booh, id: -1012, owner: 0, creator: megacz,
    membership: 0, flags: S-M--, group quota: 0.

is there a danger in doing this, other than perhaps confusion?

  - a