Ion-content in R4 child component

In my Ionic 3 app I have a hierarchical component setup whereby the ion-content (and ion-header) is only declared at the bottom level i.e in a very simplified form it looks something like this:

Component A contains:


Component B contains:


Component C contains:


I’m migrating the app to Ionic 4 at the moment and it appears that this will no longer work - I can only get something to display on the screen if the ion-content and ion-header tags are moved up to the very top level i.e in Component A. Does it make sense that this would no longer work in Ionic 4 or is there something I can do to make it work?