NSWindow contentView not cover full window size – macOS & SwiftUI

I just used the following variant in AppDelegate, the content of ContentView and others can be any

func applicationDidFinishLaunching(_ aNotification: Notification) {
    // Create the SwiftUI view that provides the window contents.
    let contentView = ContentView()
        .edgesIgnoringSafeArea(.top) // to extend entire content under titlebar 

    // Create the window and set the content view. 
    window = NSWindow(
        contentRect: NSRect(x: 0, y: 0, width: 480, height: 300),
        styleMask: [.titled, .closable, .miniaturizable, .texturedBackground, .resizable, .fullSizeContentView],
        backing: .buffered, defer: false)
    window.center()
    window.setFrameAutosaveName("Main Window")

    window.titlebarAppearsTransparent = true // as stated
    window.titleVisibility = .hidden         // no title - all in content

    window.contentView = NSHostingView(rootView: contentView)
    window.makeKeyAndOrderFront(nil)
}