Apple is very consistent with this: the visual display always indicates the current state.

Other operating systems and third-party applications are not always consistent, even some big popular ones. 1Password used a "locked padlock" icon to both mean "it's locked" and "it's not locked (click here to lock it)", for the first 12 years. (They never fixed it, though with 1Password 7 they strangely removed the lock button entirely.)

Maybe it's because I grew up using Apple computers, but I never understood why one would make a control show the state that it isn't in.