SwiftUI: withAnimation not working with App #State - swiftui

Question

I have a #State var opacity at the App level (i.e. not in a View). I would like to animate its changes. The changes do get applied (causing re-render), but it doesn't animate. I could only get animation to work when I moved that state var into the view.
Is there a way to get withAnimation to work with App state?
My reason for storing that state at the App level is, I also want to pass it to the Settings scene.
This does not work:
#main
struct MacosPlaygroundApp: App {
#State private var opacity: Double = 1.0
var body: some Scene {
WindowGroup {
ContentView(opacity: opacity, onClick: {
withAnimation(.linear(duration: 1)) {
opacity -= 0.5
}
})
}
}
}
struct ContentView: View {
let opacity: Double
let onClick: () -> Void
var body: some View {
Button("Press here") {
onClick()
}
.padding()
.opacity(opacity)
}
}
This works:
The opacity-change animates for both the button in ContentView and the shape in ChildView.
#main
struct MacosPlaygroundApp: App {
var body: some Scene {
WindowGroup {
ContentView()
}
}
}
struct ContentView: View {
#State private var opacity: Double = 1.0
var body: some View {
VStack {
Button("Press here") {
withAnimation(.linear(duration: 1)) {
opacity -= 0.5
}
}
ChildView(opacity: opacity)
}
.padding()
.opacity(opacity)
}
}
struct ChildView: View {
let opacity: Double
var body: some View {
Color.pink
.contentShape(Rectangle())
.opacity(opacity)
.frame(width: 200, height: 200)
}
}