runtime: ComWrappers instances do not provide isolation

Repro:

using System;
using System.Collections;
using System.Runtime.InteropServices;

class ComWrappers1 : ComWrappers
{
    protected override unsafe ComInterfaceEntry* ComputeVtables(object obj, CreateComInterfaceFlags flags, out int count)
    {
        throw new NotImplementedException();
    }

    protected override object CreateObject(IntPtr externalComObject, CreateObjectFlags flags)
    {
        return new ComWrapper1(externalComObject);
    }

    protected override void ReleaseObjects(IEnumerable objects)
    {
        throw new NotImplementedException();
    }
}

class ComWrapper1
{
    IntPtr _punk;

    public ComWrapper1(IntPtr punk)
    {
        _punk = punk;
    }
}

class ComWrappers2 : ComWrappers
{
    protected override unsafe ComInterfaceEntry* ComputeVtables(object obj, CreateComInterfaceFlags flags, out int count)
    {
        throw new NotImplementedException();
    }

    protected override object CreateObject(IntPtr externalComObject, CreateObjectFlags flags)
    {
        return new ComWrapper2(externalComObject);
    }

    protected override void ReleaseObjects(IEnumerable objects)
    {
        throw new NotImplementedException();
    }
}

class ComWrapper2
{
    IntPtr _punk;

    public ComWrapper2(IntPtr punk)
    {
        _punk = punk;
    }
}

class Program
{
    [DllImport("api-ms-win-core-winrt-l1-1-0.dll", PreserveSig = true)]
    internal static extern int RoGetActivationFactory(
          [MarshalAs(UnmanagedType.HString)] string activatableClassId,
          [In] ref Guid iid,
          [Out] out IntPtr factory);

    static Guid IID_IUnknown = new Guid("00000000-0000-0000-c000-000000000046");

    static void Component1()
    {
        var wrappers = new ComWrappers1();

        if (RoGetActivationFactory("Windows.UI.Xaml.Interop.NotifyCollectionChangedEventArgs", ref IID_IUnknown, out IntPtr punk) != 0)
            throw new COMException();

        var wrapper1 = (ComWrapper1)wrappers.GetOrCreateObjectForComInstance(punk, CreateObjectFlags.None);
    }

    static void Component2()
    {
        var wrappers = new ComWrappers2();

        if (RoGetActivationFactory("Windows.UI.Xaml.Interop.NotifyCollectionChangedEventArgs", ref IID_IUnknown, out IntPtr punk) != 0)
            throw new COMException();

        // Returns ComWrapper1!
        var wrapper2 = (ComWrapper2)wrappers.GetOrCreateObjectForComInstance(punk, CreateObjectFlags.None);
    }

    static void Main(string[] args)
    {
        Component1();
        Component2();
    }
}

Expected behavior: Succeeds Actual behavior: System.InvalidCastException: 'Unable to cast object of type ‘ComWrapper1’ to type ‘ComWrapper2’.