9.0-RC2 - bsdinstall - new user group

Doing a fresh install of 9.0RC2 [amd64].

Add User Accounts -> Yes

[stuff between '*' is my input/answers]

Username: *peter*
Full name: *P*
UID: [default]
Login group [peter]: *admin*
Group admin does not exist!
Login group [peter]: *ENTER*
Login group is peter. Invite peter into other groups? []?
.
..
....

Why can the installer create a new login group 'peter' but not a new login
group 'admin' ?.
  [when adding second user, I can input Login Group of 'peter' without any
problems, or third user can create a group name of its name, but still
no 'admin' group unless I add an 'admin' user].

]Peter[
  No biggie, just always have to remember to edit /etc/group.