Strange Marshalling issue

using System;
using System.Text;
using System.Runtime.InteropServices;
                    
public class Program
{
    [StructLayout(LayoutKind.Sequential, Pack = 1)]
    public struct Handle_t
    {
        public Int32 m_value;
    }
    
    [StructLayout(LayoutKind.Sequential, Pack = 4)]
    public struct Test_t
    {
        public Handle_t Test;
        
        [MarshalAs(UnmanagedType.I1)]
        public bool Test2;
        
        [MarshalAs(UnmanagedType.I1)]
        public bool Test3;
    }
    
    [StructLayout(LayoutKind.Sequential, Pack = 4)]
    public struct TestInt_t
    {
        public Int32 Test;
        
        [MarshalAs(UnmanagedType.I1)]
        public bool Test2;
        
        [MarshalAs(UnmanagedType.I1)]
        public bool Test3;
    }
    
    public static void Main()
    {
        Console.WriteLine(Marshal.SizeOf<Int32>()); // 4, OK
        Console.WriteLine(Marshal.SizeOf<Handle_t>()); // 4, OK
        Console.WriteLine(Marshal.SizeOf<Test_t>()); // 6, not OK, why? It should be 8, as Handle_t only contains an Int32, and is 4 bytes
        Console.WriteLine(Marshal.SizeOf<TestInt_t>()); // 8, as expected.
    }
}