Disconnect Mobile Broadband connection not working (C++/WinRT)

Question

I have previously used the Mobile Broadband API but recent MSDN notes suggest developers should start using the WinRT equivalent API.

Starting in Windows 10, version 1803 (10.0; Build 17134), the Win32 APIs described in this section are superseded by the Windows Runtime APIs in the Windows.Networking.Connectivity namespace.

I can successfully create a mobile broadband connection with WinRT, but have not been able to get disconnect to work.
The porting guide mobile-broadband-networks-api-porting shows that to disconnect simply call ConnectionSession.Close(), but this does not seem to do anything. I am testing on Windows 10 21H2 if that makes any difference. My sample code is as follows:

#include <winrt/base.h>  
#include <winrt/Windows.Foundation.h>  
#include <winrt/Windows.Networking.Connectivity.h>  
  
using namespace winrt;  
using namespace winrt::Windows::Foundation;  
using namespace winrt::Windows::Networking::Connectivity;  
  
int main()  
{  
    winrt::init_apartment();  
  
	CellularApnContext apn_context;  
  
	apn_context.AccessPointName(L"everywhere");  
	apn_context.UserName(L"eesecure");  
	apn_context.Password(L"secure");  
	apn_context.AuthenticationType(CellularApnAuthenticationType::None);  
	apn_context.IsCompressionEnabled(false);  
  
	auto call = ConnectivityManager::AcquireConnectionAsync(apn_context);  
	std::cout << "Connecting..." << std::endl;  
	call.get();  
  
	if (call.Status() == AsyncStatus::Completed)  
	{  
		ConnectionSession session = call.GetResults();  
  
		std::cout << "Connected!" << std::endl;  
		  
		std::this_thread::sleep_for(std::chrono::seconds(1));  
  
		std::cout << "Disconnecting..." << std::endl;  
		session.Close();   // <---- This should drop the connection!  
		std::cout << "Disconnected" << std::endl;  
  
	}  
}  

Also, why does the connection task take 30 seconds to complete when the device can connect and assign an IP in less than 5 seconds?