I agree with you, but I think the assumption here is that we're comparing two code bases that are both trying to be performant. The Rust defaults will probably start off more performant, and the ceiling will be higher as well.

A lot of the performance comes from the different paradigms though, so it's not always an apple to apple comparison. But I also think that's an assumption being made when talking about a Clojure Vs Rust implementation. In the latter, you're most likely implying using mutable collections, fixed size structs, primitive types, and a tighter memory allocation surface. And not surprisingly, those are the same changes you'd make to your Clojure code base to speed it up (most likely).