Circle() lose smoothness after .trim

Why a Circle's borders lose smoothness after trimming?

struct WidgetsEntryView : View {
    var entry: Provider.Entry

    var body: some View {
        VStack {
            ZStack {
                Circle()
                    .trim(from: 0.0, to: min(CGFloat(0.5), 1.0))
                    .stroke(Color.green, style: StrokeStyle(lineWidth: 10, lineCap: .round, lineJoin: .round))
                    .rotationEffect(Angle(degrees: 270))
            }
            Text("Subtitle")
                .foregroundColor(.white)
        }
        .padding()
        .background(Color.black)
    }
}

And why the smoothness returns after removing the text, padding or trim itself?