Demonstration of weird WKWebView behavior when paired with SwiftUI

WeView.swift

import SwiftUI

struct ContentView: View {
    @State var showModal: Bool = false

    var body: some View {
        NavigationView {
            VStack {
                WebView(url: URL(string: "https://www.example.com")!)
                Button("Fixme") { self.showModal = true }
            }
        }.sheet(isPresented: $showModal) { Text("Dismiss Me") }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

import WebKit

struct WebView: UIViewRepresentable {

    let url: URL

    final class Coordinator {
        var alreadyLoaded: Bool = false
    }

    init(url: URL) {
        self.url = url
    }

    func makeCoordinator() -> Coordinator {
        return Coordinator()
    }

    func makeUIView(context: Context) -> WKWebView {
        return WKWebView()
    }

    func updateUIView(_ uiView: WKWebView, context: Context) {
        if !context.coordinator.alreadyLoaded {
            uiView.load(URLRequest(url: url))
            context.coordinator.alreadyLoaded = true
        }
    }
}

Adding this to a new project and running it demonstrates the issue I'm hitting. When the app initially loads, the web view is inset on the top as if it's doubling up on the margin for the navigation bar. When the "Fixme" button is tapped, it corrects itself.