Hi,
Not it is not true, the best practice is to dedicate a vmnic and to have a redancy network. in fact you are in this configuration. You have a vswitch with 2 nics, and 2 port group but you are using a failover order configuration. So no need to dedicate 2 nics for your management network, one is enough. When you will loose you first nics, your host will use the second nic and it will not be in a state "disconnect".You will be in a "degraded mode" but the host will be up. I think you have something else. Are you able ping your host and your are using the second nic?
And for add your host again, you simply need to select your disconnected host, right-click and click on connect..
Regards,
Julien.