No, they're not. That's other weird policies specific to your ISP.
With IPv4 + NAT, you have a public IP address. That public address goes to your router. Your router can forward any port to any machine on your LAN. I used to run Minecraft servers from a residential connection on IPv4, it was fine. Never had to call the ISP.
With IPv4 + NAT, you have a public IP address. That public address goes to your router. Your router can forward any port to any machine on your LAN. I used to run Minecraft servers from a residential connection on IPv4, it was fine. Never had to call the ISP.