I think you are right. But as a proof of concept is an interesting read. I've work extensively with Rust and PyO3 and Maturin and even for a medium to large project is great. I wrote a bit about that here:
I've created a library using this crate (https://github.com/wiktor-k/pysequoia/) and most of the time I could just focus on the problem domain instead of technical details of the bindings.
There are just a couple of smaller issues (eg. Python to Rust async is not built in) but overall it's really nice.
I wouldn't necessarily expect a demo; but not mentioning it at all seems like it could lead readers down a path where they choose the "most performant" option presented (FFI + ctypes). The post has a "To go further:" link section where even a quick link to PyO3 would go a long way. So I thought I'd mention the downsides and an alternative on HN.