>This is spectacularly false. For all non-trivial allocation/deallocation patterns, Rust also uses a runtime reference-counting GC, which is significantly slower than the tracing GCs you find in OpenJDK.

This is not really a good comparison because you can't write the same code in either language. In Java practically everything gets allocated on the heap barring some optimizations. Meanwhile Rust programs can selectively allocate memory on the stack when it makes sense to do so. Reference counting is is just one of many different allocation strategies available to Rust. It is not the first tool you grab when you want to allocate memory in Rust, therefore absolute throughput of reference counting might not be as relevant in Rust as the absolute performance of the GC in Java.