SwiftUI var assignment simply broken under iOS14/BigSur

Unless I uncomment either the line that creates a binding in the view or the line that references the details state var in the view when I tap on the button I get a blank view under iOS 14 and MacOS 11

Under iOS 13 it shows "These are the details" string

Being a core issue this will affect a lot of the SwiftUI code, what makes it worse is that in views with a Binding it will work properly so its even harder to spot.

Code Block 
struct MyViewController : View {
    @State var details: String?
    @State var showDetails = false
    //    @Binding var havingAbindingFixesIt: String?
    var body: some View {
        VStack {
            //            Text(details ?? "")
            Text("Tap here for details")
                .onTapGesture {
                    self.details = "These are the details"
                    self.showDetails.toggle()
                }
                .sheet(isPresented: $showDetails) { Text(details ?? "") }
        }
    }
}