Thank you for your answer.
The reason GetProperty is marked as deprecated is that you don't
it with GetProperties(). Your client should use GetProperties() once at
boot up to get the complete state and then just listen to properties
change events. The problem using GetProperty() is that the client gets
easily out of sync with the states.
Allright, it makes totally sense now.
The commentary "Use the Manager.GetServices() method instead."
can be misunderstood, as it does not mention that the client shall
only do one initial call to GetServices and trigger PropertyChanged or
ServicesChanged signals to update a local Services properties database.
For project matter, we will continue to use the GetProperties(), by our side,
but the patch is irrelevant.