I’d imagine almost any old model could do this?

Why even waste money on an LLM. Just lorum ipsum the content since nobody is going to read it anyway

but a model could write blog posts that describe changes to the website as a blog-style changelog (e.g., 'today i spent an hour playing with CSS to change padding' or 'i refactored the backend to do more async calls')

a self-documenting blog about the blog.

\lipsum has been perfectly good at that for decades