Early on in the blog post, the author mentions that "c2rust can produce a mechanical translation of C code to Rust, though the result is intentionally 'C in Rust syntax'". The flow of the post seems to suggest that LLMs can do better. But later on, they say that their final LLM approach produces Rust code which “is very 'C-like'" because "we use the same unsafe C interface for each symbol we port”. Which sounds like they achieved roughly the same result as c2rust, but with a slower and less reliable process.
It’s true that, as the author says, “because our end result has end-to-end fuzz tests and tests for every symbol, its now much easier to 'rustify' the code with confidence". But it would have been possible to use c2rust for the actual port, and separately use an LLM to write fuzz tests.
I'm not criticizing the approach. There's clearly a lot of promise in LLM-based code porting. I took a look at the earlier, non-fuzz-based Claude port mentioned in the post, and it reads like idiomatic Rust code. It would be a perfect proof of concept, if only it weren't (according to the author) subtly buggy. Perhaps there's a way to use fuzzing to remove the bugs while keeping the benefits compared to mechanical translation. Unfortunately, the author's specific approach to fuzzing seems to have removed both the bugs and the benefits. Still, it's a good base for future work to build on.