If the device can't communicate outbound then no you're completely safe. There's no magic into this, hole punching is just a silly name for a simple technique.

If the device can't communicate outbound then no you're completely safe. There's no magic into this, hole punching is just a silly name for a simple technique. Hole punching works when both A and B are behind NAT. It also allows B to contact A if A is behind a NAT (no matter if B is behind one or not). If both A and B have public IP's then the hole punching is "already done", they can already connect to eachother.