Rust-analyzer doesn't enable a dependency feature as expected

[4JX]

I have "rust-analyzer.cargo.features": ["scrap/linux-pkg-config"] in a .vscode/settings.json, but it seemingly doesn't want to work.

Manually running the command does:

» cargo check --workspace --message-format=json-diagnostic-rendered-ansi --manifest-path /path/to/Cargo.toml --keep-going --all-targets --features scrap/linux-pkg-config
(whole load of diagnostics text)

Build script fails on this function, with VCPKG_ROOT not found..., which is code it shouldn't be getting to given that using pkg-config is enabled and I'm not setting NO_PKG_CONFIG_* anywhere.

Am I doing/expecting something wrong? Or is the issue elsewhere?