VaadinSession and idle timeouts

I’m very confused about current (actually V23 flow) VaadinSession lifecycle and could use some suggestions.
In the “normal” situation, our application is set up to time out after 15 minutes of idle user time: it works great even with multiple UI scopes, and we get a SessionDestroyEvent on the enclosing VaadinSession when we time out.
The application also has a little floater popup that users can display showing a status of various backend things, refreshed by a daemon thread. When the user has that going, and we idle timeout things get strange: we do get a SessionDestroyEvent, but it is with an unauthenticated VaadinSession instance - the actual session running the UI never gets timed out while the floater is running.