you mean a relay right?

in my relay it's not a requirement, but because there's no way for the client to initiate the AUTH my relay needs to send an AUTH out of the gate but if the client doesn't want to AUTH it's fine, they can keep using the relay, just with a "limited" view

whereas if a relay tells you "auth-required" that's a more explicit signal that you need to AUTH to talk to it (or at least to execute that filter)