The standard library exposes an API for some of them, and you can access the internal data-structures of the Rust by adding a line to your program to import them (requires unstable Rust) or by adding a line to your Cargo.toml to load them from crates.io.

The argument is flawed in that these are set in stone in any practical way. This is because Rust binaries do not run on a whiteboard, they run on real hardware, which means that there are thousands of different ways to efficiently implement these data-structures depending on what your precise use case is, and most of them affect their API design. For example, while Rust is lucky enough to provide a HashTable with a Google Swisstable-compatible API, C++ std::unordered_ containers are not, and cannot be upgraded.

The argument is also flawed into assuming that Rust is a static language. It isn't, the language is evolving, and as the language evolves the requirements on the internal data-structure changes, resulting in changes to the algorithms and data-structures being used (not only their implementation).

For example, at the end of last year Rust shipped non-lexical lifetimes, which uses a complete different borrow checking algorithm, data-structures, etc. The old ones just are not compatible with it.

Then there is also the fact that many people work on improving the performance on the Rust compiler. This means that the graph data-structures used are often not generic, but exploit the graph structure and the precise type of the graph nodes. As these data-structures are parallelized, made cache friendly, allocation-free, exploit usage of other platform-specific features like thread-locals, atomics, ... their APIs often changes. Also, often somebody just "discovers" that there are better algorithms and data-structures for implementing one pass, and they just change them.

Putting these in the standard library incurs a massive cost since this makes them almost impossible to evolve inside the Rust compiler, adds a huge maintenance cost, etc. And for what value? If you want to precisely use what the Rust compiler uses, you can already add a line to your program to import that from somewhere else that makes it clear that these are not stable. If you want general graph data-structures, chances are that your graph won't look like the ones used by the rust compiler. There are hundreds of crates for manipulating graphs in crates io, depending on how big the graphs are, whether you can exploit some structure, the common operations that you want to do with them, etc.

Sure, on the whiteboard, all of them probably have the same or similar complexity-guarantees, but on real hardware constant factors make a big difference for real problems.