WGM / “Show computer’s administrators” not working for OD accounts.

The "Show computer's administrators" setting in WGM/"Computer Group Preferences"/Login/Window/"List of users able to use these computers" doesn't seem to affect OD accounts set up as local administrators. In 10.5.4 I've set up an ACL for computer groups with one user as an admin. I would like to show available accounts but would like to exclude the admin account from being shown in the login window. Can anyone verify this behavior, ......or know of a way to do this?