Cannot align ScrollView to the top

You used Vstack and Spacer to align the area of the horizontal scroll view to the top. Please check if the implementation you want is correct.

import SwiftUI

struct ContentView: View {

    private enum Constants {
        static let cellSize = CGSize(width: 100.0, height: 100.0)
        static let rowSpacing: CGFloat = 8.0
    }


    @State private var rowCount = 1
    @State private var contentOffset = CGPoint.zero

    private var scrollViewHeight: CGFloat {
        CGFloat(rowCount) * Constants.cellSize.height + (CGFloat(rowCount) - 1.0) * Constants.rowSpacing
    }

    var body: some View {
        NavigationView {
            VStack {
                ScrollView(.horizontal) {
                    ScrollView {
                        LazyVStack(spacing: Constants.rowSpacing) {
                            ForEach((0..<rowCount), id: \.self) { _ in
                                LazyHStack {
                                    ForEach((1...20), id: \.self) {
                                        Text("Cell \($0)")
                                            .frame(
                                                width: Constants.cellSize.width,
                                                height: Constants.cellSize.height
                                            )
                                            .background(.red)
                                    }
                                }
                            }
                        }
                    }
                    .scrollIndicators(.hidden)
                }
                .background(.cyan)
                .ignoresSafeArea(edges: .bottom)
                .frame(maxHeight: scrollViewHeight)
                .scrollIndicators(.hidden)
                .toolbar {
                    Button("Add Row") {
                        rowCount += 1
                    }
                    Button("Remove Row") {
                        rowCount -= 1
                    }
                }
                .navigationTitle("Test")
                Spacer()
            }

        }
    }
}

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