I'm seeing inconsistent results with different types of Binding<>

I've created a UserDefaults extension to generate custom bindings.

extension UserDefaults {
    func boolBinding(for defaultsKey: String) -> Binding<Bool> {
        return Binding (
            get: { return self.bool(forKey: defaultsKey) },
            set: { newValue in
                self.setValue(newValue, forKey: defaultsKey)
        })
    }
    func cardPileBinding(for defaultsKey: String) -> Binding<CardPile> {
        return Binding (
            get: { let rawValue = self.object(forKey: defaultsKey) as? String ?? ""
                return CardPile(rawValue: rawValue) ?? .allRandom
            },
            set: { newValue in
                self.setValue(newValue.rawValue, forKey: defaultsKey)
        })
    }
}

For the sake of completeness, here is my enum

enum CardPile: String, CaseIterable {
    case allRandom
    case numbers
    case numbersRandom
    case daysMonths
    case daysMonthsRandom
}

I've also created UI elements that use these bindings:

    var body: some View {
        VStack {
            Toggle("Enable", isOn: UserDefaults.standard.boolBinding(for: "enable"))
            Picker("Card Pile", selection: UserDefaults.standard.cardPileBinding(for: "cardPile")) {
                ForEach(CardPile.allCases,
                        id: \.self) {
                    Text("\($0.rawValue)")
                        .tag($0.rawValue)
                }
            }
        }
    }

When I tap the toggle, it updates correctly. However when I tap the picker and select a different value, the binding setter gets called, but the view does not refreshed to reflect the change in value. (If I force quit the app and re-run it, the I see the change.) I would like to find out why the Binding<Bool> works as I'd expected (ie updates the UI when the value changes) but the Binding<CardPile> behaves differently. any/all guidance very much appreciated. Note: I get the same behavior when the enum use Int as its rawValue