StructureMap Container returning Multiple Proxy Instances for Singleton Registration

Question

I am using StructureMap for resolving the Dependency in my Projects, I am getting multiple Proxy instances for a Singleton Registration while resolving, below are the code

in StartUp.cs file I am creating a new container and adding one Policies as per below code

var structuremapContainer = new Container();
structuremapContainer.Configure(
    x => x.Policies.Interceptors(new ProfilerInjectorPolicy()));

ProfilerInjectorPolicy.cs

public class ProfilerInjectorPolicy : IInterceptorPolicy
{
    private static readonly ProxyGenerator _proxyGenerator = new();
    private static readonly MethodInfo _genericProxyDelegate =
        typeof(ProfilerInjectorPolicy)
            .GetMethod("GetProxy", BindingFlags.NonPublic | BindingFlags.Static);

    public string Description => "Profiler injector policy";
    
    public IEnumerable<IInterceptor> DetermineInterceptors(
        Type pluginType, Instance instance)
    {
        var interceptorType =typeof(FuncInterceptor<>).MakeGenericType(pluginType);
        var method = _genericProxyDelegate.MakeGenericMethod(pluginType);
        var arg = Expression.Parameter(pluginType, "x");
        var methodCall = Expression.Call(method, arg);
        var delegateType = typeof(Func<,>).MakeGenericType(pluginType, pluginType);
        var lambda = Expression.Lambda(delegateType, methodCall, arg);
        var interceptor =
            Activator.CreateInstance(interceptorType, lambda, string.Empty);
        yield return interceptor as IInterceptor;
    }

    private static T GetProxy<T>(object service)
    {
        var allInterfaces = service.GetType().GetInterfaces();
        var additionalInterfaces = allInterfaces.Except(new[] { typeof(T) });
        var result = _proxyGenerator.CreateInterfaceProxyWithTargetInterface(
            typeof(T),
            additionalInterfaces.ToArray(), service, new ProfilerInterceptor());   
        return (T)result;
    }
}

Problem is, when I am Registering as a Singleton with Func<> Object, The GetProxy() method call everytime while resolving the dependency, I have tested that it's only calling the GetProxy() method, but not calling the constructor of class except first time.

yield return Registration.AsSingleton(typeof(IProduct), () => new Product());

This return the new Proxy instance on every time when calling Container.GetInstance<IProduct>().

yield return Registration.AsSingleton<IProduct, Product>(); This call only once the GetProxy() method on every time when calling Container.GetInstance<IProduct>().

Can anyone help me why I am getting this issue, is there anything I need to change in my code.

// This should call once the GetProxy() method like
yield return Registration.AsSingleton<IProduct, Product>(); 
yield return Registration.AsSingleton<IProduct, Product>();