Account – display name dropdown issue

I’m seeing a minor bug with the Account – Display Name drop down.
I see that it has option to choose Username, Nickname, First/Last Name.
I don’t want the Nickname as option for users to use or display (only want users to display Username or First/Last Name), so under Users > Custom Fields, I set Nickname Privacy: hidden, Permissions: hidden
Then when I view account, the Nickname field is gone, but the Nickname is still in the drop-down menu. If I select it and save profile, nothing happens (as expected). I think the Nickname option from drop down should be removed if its a hidden field, since it can’t even be set as Display name.