The publishing application can be used with multiple views open at the same time on several different tabs or browser windows, but it can also be used simultaneously on several different devices. On one device, or more precisely, on one browser, user first have to log in with a password, after which user is presented with a login session code, which can be used to log in to the publishing application with the same username on an unlimited number of browsers. When a view of the user interface of the publishing application is just open and visible, it is not using server resources at all.
This can be useful, e.g. when writing on one device, such as a laptop, while at the same time holding a tablet-type device in portrait mode with some notes visible on it. An alternative to just that would be to use one login and an extended desktop with e.g. a monitor connected to the HDMI connector. Or maybe user want to have two different devices with the publishing app ready to use, but uses only one device at a time. One log out is sufficient. No need to do it on every browser/device.