Yep. It’s not clear to me that replication needs to be an official feature at all, tbh. You don’t need it and shouldn’t use it.
We kinda need it due to the peculiarities of supporting a million+ clients, but short of that it’s always better, simpler and more robust to just run two separate servers with no replication.
And if you’re running that large a Syncthing network in secret then you should probably just fork the discovery server and do what you need for your infrastructure.
To be fair though: I wouldn’t have stumbled across this, hadn’t the CLI params for stdiscosrv changed. I used the (now defunct) -replication-listen param to disable the port binding (default “:19200”), which I think is good practice, if you do not use something (which I didn’t).
That being said: I do make it a good practice to understand what the software I run is doing (or can possibly do). Keep in mind also, that people running their own discovery/relay server do not use your infrastructure, which is a good thing for you.