It didn't read as LLM-generated to me. And having some experience with CMS development, the article has plenty of substance. You can check previous blog articles from the same author far predating LLMs - here's one from 2018:
https://www.sanity.io/blog/getting-started-with-sanity-as-a-.... The main difference i see with the OP article is it's a bit more emotive - probably a result of responding to a public trashing of their product.
The main point I'd like to raise in this comment though is that one of us is wrong - maybe me or you - and our internal LLM radar / vibe check is not as strong as we think. That worries me a bit. Probably LLM accusations are now becoming akin to the classic "You're a corporate shill!".