vApp networks must connect to Org network?

I have setup my test environment and have created a vApp network that is not connected to an Org net.   In theory this is a vApp isolated network,   but viewing the PortGroups in my vDS,  I see that a vApp portgroup is not created for this vapp network.   Without backing of a portgroup the vApp VMs would not be able to communicate with eachother if they land on different hosts,  right?

So while it is possible to setup "isolated" vApps this way,  it would not be practical as the VMs would not be able to communicate?

Thanks,

-Matt