Why does the NotificationService obtain the viewContainerReference through dependency injection, whereas the ModalService uses the PlaceHolderService to retrieve the ViewContainerRef?

[csikb]

I'm migrating a project from v4 to v5 and the NotificationService seems to be broken for me. The NotificationModule and the PlaceholderModules are imported at the Application Module level. And I inject the NotificationService into application Components and Services.