I'd assume that the only reason one would need to know if chunks were incoming is to indicate a loading state in disparate parts of your webpage, e.g. chunk B h

I'd assume that the only reason one would need to know if chunks were incoming is to indicate a loading state in disparate parts of your webpage, e.g. chunk B has some widget that indicates chunk A is loading. In this case, you can probably work off the assumption that loading is the default initialization state, and use JS to communicate to the disparate parts of your page once on chunk A load. There may be something different that you're thinking about here though.