Docker docs:
Docker routes container traffic in the nat table, which means that packets are diverted before it reaches the INPUT and OUTPUT chains that ufw uses. Packets are routed before the firewall rules can be applied, effectively ignoring your firewall configuration.
This only happens if you essentially tell docker "I want this app to listen on 0.0.0.0:80"
If you don't do that, then it doesn't punch a hole through UFW either.