I think this article is specifically about running web servers inside of networks with firewalls that block udp on port 443 for whatever reason. There are lots

I think this article is specifically about running web servers inside of networks with firewalls that block udp on port 443 for whatever reason. There are lots of older networks that have such firewalls and they aren't going to get upgraded overnight. Reaching http3 servers outside those networks is indeed not a problem as the connection gets downgraded appropriately. You'd know this when Google, for example, stops working inside your network as most of their load balancers are serving http3. Users tend to complain about these things and this obviously hasn't been happening. Ergo, connections are being downgraded as you'd expect. But putting up webservers serving http3 in a network that blocks udp3 is indeed not going to work until somebody fixes the firewall. You could still do it and test if browsers from outside the network downgrade correctly. But that seems a bit pointless.