Comment by nmadden
The way DH is used typically for encryption (ECIES) or in TLS doesn’t give you authentication. But you can get authentication from DH alone, without PSK or PKI. See https://neilmadden.blog/2021/04/08/from-kems-to-protocols/ for some details on the security properties of various types of DH.
I meant that some data still needs to be distributed securely, just it's the sender's public key rather than a PSK. I recon "pre-shared data" was not the best choice of words...
(Still love the blog post!)