Codecs are actually a wonderful test-case for Rust: they're a frequent source of vulnerabilities because they have to deal with arbitrary input, they usually have to perform fiddly sub-byte and/or array manipulation, and their pressure for maximum performance mean they have to make as efficient use of the hardware and memory as possible (and any mistake lead back to the first point)

So even if you don't agree with some of the author's points, his use-case is a good test for the suitability of Rust as a Systems Programming Language.