为什么在添加本地引用时，GAC的ASP.NET网站引用程序集？

When you use ASP.NET web site (instead of web application model) and add reference to an assembly from local folder, Visual Studio, it seems, understands that this local assembly is also in GAC and so does NOT copy this assembly to bin folder (as it does with non-GAC assemblies), but simply adds new record in web.config file. When you use ASP.NET web site (instead of web a