admin protected but can still change password

I have three roles: administrator/maintainer/authenticated user
There is only one user in the role called administrator, and that user is called admin.

I log in as a user with the role maintainer.

example.com/admin/people
click on "edit" for user "admin"
I get the following message that I would expect:
"admin has been protected from the following editing operations: username, e-mail, status, roles, cancel"

If I click on the "password" tab, I can then change the password for user "admin". There is no warning message and the system doesn't stop me.

Can anyone suggest what I'm doing wrong?

configuration as follows:
in PROTECTED USERS:
admin: user, email, password, status, roles, cancel are all checked
there are no other protected users

in PROTECTED BY ROLE:
administrator: user, email, password, status, roles, cancel are all checked
nothing is checked for other roles

in ADMINISTRATOR BYPASS:
admin has all items checked.
no other user has been added

in PROTECTION DEFAULTS:
only status and cancel in User protection defaults are checked
nothing else is checked

in PERMISSIONS:
maintainer cannot administer permissions, but can do all other user functions