The technology that article mentions is Microsoft's Intel->ARM translation, which is surprisingly good, and entirely unrelated to Firefox.
The "optimized" build they're talking about is almost certainly natively-compiled ARM64, and the reason it's hard is because Rust is built on an older llvm version...which doesn't have Google's patches that improve support for Windows ARM64.
The technology that article mentions is Microsoft's Intel->ARM translation, which is surprisingly good, and entirely unrelated to Firefox.
The "optimized" build they're talking about is almost certainly natively-compiled ARM64, and the reason it's hard is because Rust is built on an older llvm version...which doesn't have Google's patches that improve support for Windows ARM64.