Earlier quoted context omitted.
My understanding is that docker will expose the ports to the host machine's network interfaces, which is a crucial difference. For my home server running docker that means exposed to the LAN, but not the WAN unless I add in a port forwarding rule on my router. Similarly in an enterprise environment you would be exposing the port on whatever VLAN the host is connected to, which hopefully doesn't have directly transit…
I was thinking along similar lines to what you've suggested here, but then I considered how many VPS might be configured by folks following some random web tutorial, to set up their LAMP stack (or whatever), that end up doing something like what was described.
A lot of those VPS instructions these days recommend a reverse proxy like Caddy or Traefik for that exact reason. I think it's also a valid argument to say that anyone playing around on a VPS without knowing what they're doing is probably going to learn some hard lessons, and that's kind of the point.