I'd say Scala's support for scientific computing is significantly ahead of Rust; there are good libraries for ML, linear algebra and what have you (including relatively good bindings for native LAPACK), and there's the whole Spark ecosystem.

Scala on a well-tuned JVM can reach much lower latency than you might think. Yes, in theory you'll hit a limit that Rust could help you go beyond. In practice, are you ever going to reach that limit?

Rust's embedded support is mostly theoretical at this point, and the use cases for old-school embedded are increasingly limited. Want to write some code for that cheap off-the-shelf SoC you bought? Scala is probably a perfectly good option, because it's probably an ARM with at least 1Gb of RAM and the JVM will run there just fine. If you're actually writing something that has to run for months off a single charge then yeah, Scala won't cut it whereas Rust may one day be able to. But most "embedded" these days isn't like that.