Programming language power efficiency always feels like the tech industry green washing if I'm being honest. It always comes and goes on a pretty predictable year or two cycle.
A data center switching everything to Rust won't use less power than running Java, as the companies running these resources hogging computing warehouses will just use the reduced overhead to further expand their through-put.
Training AI crap will always use astronomical compute resources because they'll use everything they can usurp regardless of language.