Not at all an expert on this, but my impression is the trust model is different for IPFS than for the web. IPFS is a distributed CAS, so the address is the hash of the content (this can be verified by the client). Whereas the web focuses on "I'm talking to who I think I'm talking to", IPFS focuses on "I'm getting the content I asked for". So, to answer your question, I think authorship is an orthogonal concern to IPFS's focus, which is verifiably delivering the requested bytes.
All that said, IPNS likely bridges the content/authorship gap you're asking about.
> A name in IPNS is the hash of a public key. It is associated with a record containing information about the hash it links to that is signed by the corresponding private key. New records can be signed and published at any time.
https://docs.ipfs.io/concepts/ipns/
In this context, that key would be held by the author, allowing the author to publish different content by signing it with the key.