Do you mean a configuration profile that determines List of users vs Name and Password under the Users & Groups Login Option under system preferences? Also, is it a Configuration Profile or Managed Preference that is pushing this setting. If it is a Configuration Profile, make sure the scopes aren't conflicting.
Good being that it is a configuration profile. Can you verify that the profile actually made it to the Macs in question? (System Preferences > Profiles) Also, are you using FileVault to encrypt your macs? As FileVault will cause the List of users vs the Name and Password text field input.