Is GeometryReader (SwiftUI) in a Live Activity broken?

Question

I'm working on a LiveActivity for an iOS 16 app using SwiftUI. I can't figure out what's going on with the GeometryReader. I'm trying to get the dimensions of the entire LiveActivity view.

In Example (A) below, I've got a VStack which is set to take up max width and height and contains a GeometryReader. I'm expecting to see geo.size.height be 160 (that's the max height of a LiveActivity on an iPhone 14 Pro Max).

Weirdly, as soon as I include the GeoReader either here or virtually anywhere else in the view tree, the LiveActivity view height collapses to 64 regardless of any changes in any other views.

//EXAMPLE (A)
struct LiveActivity: Widget {
    var body: some WidgetConfiguration {
        ActivityConfiguration(for: Attributes.self) { context in
            VStack{
                GeometryReader { geo in
                    Text("Geo Height \(geo.size.height)") //REPORTS 64
                }
            }
            .frame(maxWidth: .infinity, maxHeight: .infinity)
        } dynamicIsland: { context in
            ...
        }
    }
}

//EXAMPLE (B)
struct LiveActivity: Widget {
    var body: some WidgetConfiguration {
        ActivityConfiguration(for: Attributes.self) { context in
            VStack{
                Text("Example A")
            }
            .frame(maxWidth: .infinity, maxHeight: .infinity)
            .overlay{
                GeometryReader { geo in
                    Text("Geo Height \(geo.size.height)") //REPORTS 160
                }
            }
        } dynamicIsland: { context in
            ...
        }
    }
}

I've tried all manner of ways to get everything to expand to the full size but having the GeoReader anywhere involved somehow negates everything else.

Is this a bug? Is this expected behaviour and I'm missing something? I would expect Example A to report 160 and be the full size.