An update won’t change this visual thing.
You will always see the state you’re going to change to (e.g. an internal article) just like the text next to the icon indicates.
According to the user documentation (see screenshot and link) it behaves differently.
The lock is closed for internal messages and open for public messages.
Maybe this has changed and wasn’t reflected to the documentation. Don’t know. That screenshot was created by me back in the days so it may be outdated by now… there was several changes around this icon because people got confused (several times…)