Isn't any equivalent system going to have more statements in Rust than it would have in Go?

Yes, and that's the case I've seen as well. I would also say rust is also more heavy on symbols, which can make code look kinda hard to parse in places.

But weirdly Opus (N=1) in Claude Code does okay on it. Enough I can reliably have it write software and feel confident it works.

Why would you think so? Rust provide better type system and abstraction mechanisms compared to Go, hence equivalent system should have less lines of code, at least in from my experience.