What nostr:npub1cgd35mxmy37vhkfcmjckk9dylguz6q8l67cj6h9m45tj5rx569cql9kfex meant is that he is not proposing that Nostr users have subkeys for themselves, just encryption keys that they use to encrypt messages in a group. The goals are very different and in this case it doesn't pose any problems to the protocol.