The difference between OWIN and IIS on handling HTTP HEAD request when the api is not support the HEAD request

Question

I have a 2 services(WebApi), one is azure cloud service that using IIS host and another one is azure service fabric stateless service that using Owin host. There is a handler that like below, and both services register this handler to handle the context(config.MessageHandlers.Add(new ContextHandler())).

Currently, what I met is: If I call cloud service api(just ping) using HTTP HEAD request, this will return '405 method not allowed'. But if I call fabric service, I will get 'Could not get any response' with 'there was an error connecting to...'.

When debug the code. For the cloud service using IIS, in the below code, the response.Content has no value. But for the fabric service using Owin, the response.Content has value '405 Method not allowed'.

My question is, what the difference between them? Why the Owin will return a response with content back as the request is HEAD request?

Thanks.

public class ContextHandler : DelegatingHandler
    {
        protected override async Task<HttpResponseMessage> SendAsync(
            HttpRequestMessage request, CancellationToken cancellationToken)
        {
            // initialize context
            using (new ApiRequestContextWrapper(request))
            {
                var context = ApiRequestContext.Current;
                context.Log.Trace(
                    $"API Call {request.Method.Method} 
               {request.RequestUri.GetLeftPart(UriPartial.Path)}");

                var response = await base.SendAsync(request, 
                cancellationToken).ConfigureAwait(false);                

                return response;
            }
        }
    }