Indeed, this is the intended interpretation of "Kagi's implementation of Privacy Pass" - we're talking about building out the server infrastructure, the UX, the browser extensions, the mobile applications, the Orion browser integration, the support and documentation, the Tor service, etc. The cryptography is obviously an extremely important piece, but it is far from the only piece.
As other commenters have noted, the code in question is MIT licensed [1] and we're pulling it in as a standard dependency [2], it's not like we've gone out of our way to obscure its origin. The MIT license does not require us to do anything more.
That said, I can understand the author wanting more visible attribution, and that's very reasonable, we'll add a blurb to the blog post acknowledging his contribution to Kagi's deployment of Privacy Pass.
[1] https://github.com/raphaelrobert/privacypass/blob/main/LICEN...
[2] https://github.com/kagisearch/privacypass-lib/blob/e4d6b354d...