[rise-remold]

It's because this isn't a Discord API component, this is their "voice" server of which they have hundreds deployed across the world.

Their voice server only checks with the API to verify if you're allowed to join. Beyond that, it becomes a one-to-many packet broadcaster.

[imtringued]

I don't know about "voice servers" but if you use something like coturn, there is no way to finely tune this, because it is just a generic "gateway" that is relaying packets to bypass NAT. You could try to connect to the stream and then check the stream quality after the fact but if there are false positives you are mistreating paying customers, which you certainly don't want to do.