More like an extension based off of the specs that is less likely to only lead to protocol decay and whack-a-mole development. On the basis that the current specs are too flexible. #ActivityPub is de facto a protocol framework. An extension can be the protocol with more rigor, and help ease solution development on top of that with yet more composable extensions.
W3C specs give us conceptually 'addressible actors that exchange activities with object payload'. That's powerful.