WB 2.8.1 Revision 1287 - Change group access bug?

[thea]

Is this a bug?

Fresh WB 2.8.1 Revision 1287 installation. Added 2 user groups and 2 users.
user 1 depend to group 1, user 2 to group 2

Added 3 pages, page 1, page 2, page 3

Access/edit page 1 = user 1
Access/edit page 2 = user 2
Access/edit page 3 = user 1 + 2

At screen "Modify Page Settings" 3 select-boxes appear under "Administrators:
[X] Administrators
[X] Group 1
[ ] Group 2

Why is it possible to select Group 2 for User 1. Where can i change the visibility of the Administrators column?

Best regards,
Thea