Can I ignore safe area when resizing a window in macOS 15?

I am attempting to make a macOS app to show a large popup with no titlebar and a transparent background that spans the entire active display.

Currently, I am attempting the last part, with the sizing. I used an example on the relevant developer documentation page. This is the code I am using in my App struct:

@main
struct MakeGoodChoicesApp: App {
    ...
    var body: some Scene {
        ...
        Window("Make Good Choices", id:"popup") {
            PopupWindowContentView()
                .ignoresSafeArea(.all)
        }
        .windowIdealPlacement {_, context in
            return WindowPlacement(
                x: context.defaultDisplay.bounds.minX,
                y: context.defaultDisplay.bounds.minY,
                width: context.defaultDisplay.bounds.width,
                height: context.defaultDisplay.bounds.height
            )
        }
    }
}

When running my application and using some code to open the popup window, I get the following result:

I would expect the window to expand past the safe area, but it seems as if macOS clamped the window's size down to inside the safe areas.

I would appreciate any help, many thanks!