CsWinRT doesn't generate code for IMapChangedEventArgs

[hez2010]

The below code make CsWinRT produce invalid code:

public partial class ObservableDictionaryChangedEventArgs : IMapChangedEventArgs<string>
{
    public ObservableDictionaryChangedEventArgs(CollectionChange change, string key)
    {
        this.CollectionChange = change;
        this.Key = key;
    }

    public CollectionChange CollectionChange { get; private set; }
    public string Key { get; private set; }
}

where CsWinRT generates code for ObservableDictionaryChangedEventArgs :

using static WinRT.TypeExtensions;

namespace App1
{
[global::WinRT.WinRTRuntimeClassName("Windows.Foundation.Collections.IMapChangedEventArgs`1<String>")]
[global::WinRT.WinRTExposedType(typeof(ObservableDictionaryChangedEventArgsWinRTTypeDetails))]
partial class ObservableDictionaryChangedEventArgs
{
}

internal sealed class ObservableDictionaryChangedEventArgsWinRTTypeDetails : global::WinRT.IWinRTExposedTypeDetails
{
    public global::System.Runtime.InteropServices.ComWrappers.ComInterfaceEntry[] GetExposedInterfaces()
    {
        _ = global::WinRT.GenericHelpers.IMapChangedEventArgs_string.Initialized;

        return new global::System.Runtime.InteropServices.ComWrappers.ComInterfaceEntry[]
        {
            new global::System.Runtime.InteropServices.ComWrappers.ComInterfaceEntry
            {
                IID = global::ABI.Windows.Foundation.Collections.IMapChangedEventArgsMethods<string>.IID,
                Vtable = global::ABI.Windows.Foundation.Collections.IMapChangedEventArgsMethods<string>.AbiToProjectionVftablePtr
            },
};
        }
    }
}

but there's no IMapChangedEventArgs_string being generated.

Version used: CsWinRT 2.1.0-prerelease.240602.1