Rust really has not had any presence in AI training engine yet, it's probably 100% c++.
I was referring to the libtorch library, which you can use through the tch crate. It is possible to make such rich bindings because so much of Torch is exposed through the C++ API. When more new functionality is moved to Python, it makes it harder to use functionality from the C++ interface and downstream bindings.
Or even train in C++ or Rust without much loss in functionality.