Yeah, this is happening again and again in Rust: people publish Rust benchmarks without optimization on. In fact, we just decided this week to change "Compiling" to "Compiling (Debug)" in Cargo if optimization isn't turned on to address this problem. It's sad :(
If it helps it doesn't happen only to Rust but to all languages.
There is this misunderstanding between implementations and languages where people equate whatever they have installed on their computer with all implementations of the said language.
Also not knowing about profilers and optimization flags.