Hey there! Usually, in a typical configuration Nginx takes over listening duties on ports 80 and 443, and then proxies the traffic to Apache, which is now listening on ports 444 and 81. I suppose a direct request to 444 would be handled well, but that would need to be done manually as browsers and computers aren't going to use that port for anything.
It's just like how you can configure Exim for an alternate port - it will still listen and accept mail on port 26 from a client, but communication between servers still needs to happen on port 25.