Is it possible to logout from an app or website on offline mode?

Just wanna gauge your thought on this issue. Recently, I tested an app and when I logged out in offline mode (i.e. no Internet connection), the app is, to my amazement, ABLE to log out. Furthermore, the client said it was an expected behavior! I'm a bit bemused because usually when we log out from an app/website by disabling the Internet connection, it should throw out an exception like "There is no Internet connection", right? Surely there must be a validation token in place.

Many thanks indeed.