Some would argue that Rust's advantages over C (or other languages) are so great that it constitutes a crucial feature of the software, and that while it doesn't necessarily indicate quality, it makes building quality software substantially easier.
Then shouldn't there be some observable (better yet, measurable) side effects?
True — one can certainly write terrible software in Rust, but in my view, being written in Rust is a notable enough aspect to a project to point it out