DID Core suggests that applications require the
alsoKnownAs relationship to be confirmed/reciprocol. In that case, the relationship is broken if either DID document is updated to remove that relationship. I think it is up to applications to further specify it. I'm not aware of existing applications using
alsoKnownAs, as I have not looked into this.
That sentence about revocation is about verification methods. A verification method is typically a public key. A DID Document may contain verification methods for specific purposes. Revoking a verification method would mean updating the DID document to remove that verification method id and/or object from the DID document.
It would also make sense to remove an
alsoKnownAs relationship to a DID whose verification methods are believed to be compromised. That would be done by updating the DID document to remove the ID from the