Well I Googled myself since I was curious

This comment says Rust's type inference is not Hindley-Milner, but rather it's "influenced by" bidirectional type checking: https://lobste.rs/s/hbzctm/type_inference_rust_c

(but I think that is about type inference; I think there are parts of the Rust's type checking algorithm that could be described with different terms)

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This post quotes Chris Lattner on Swift, saying

https://danielchasehooper.com/posts/why-swift-is-slow/

My experience with Swift is we tried to make a really fancy bi-directional Hindley-Milner type checker

So I guess this hints at what I suspected -- that people mean different things when they say "bidirectional"

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But also, it's probably reasonable to put Go and Zig (?) in one category, and Swift and Rust in another