Author addressed this on a Reddit comment thread: https://www.reddit.com/r/rust/comments/fbu5tt/expressjs_vs_a... . The results aren't significantly different; Rust is still very much more efficient than NodeJS especially when considering memory utilization (and the hosting costs associated with that memory footprint).
I tried to make changes and run his benchmarks, however the DB seeding is in Rust and it fails to compile on my machine....