about presentationDetents modifier

    @State private var showSheet = false

    var body: some View {
        Button("show Sheet") {
            showSheet.toggle()
        }
        Spacer()
        .sheet(isPresented: $showSheet) {
            VStack {
                Text("this is Sheet")
                    .font(.title)
                Button("close") {
                    showSheet = false
                }
            }
            .presentationBackground(Color.white.opacity(0.8))
            .presentationDetents([.medium])
            
        }
    }
}

(sheet is full screen width on ios 18.6)

(sheet is not full screen width)