No properties are actually making use of the ViewModel/[Reactive] concepts, where normal properties might change after the fact, and users might want to construct an Rx observable from a property and its changes, or a GUI might want to watch (via notifypropertychange) changes.
All concepts that are mutable and want to be followed are already able to do so without the ViewModel concepts, as the implement IObservable (IsLoggedIn, for ex)
ViewModel ideally should only be used in a GUI, as it's the weird marriage of Rx + real properties that XAML can bind to. The ViewModel is the hybrid glue to bring those two worlds together. In a situation with no GUI, it's unnecessary
