they kinda mention this - one of those is Rust, other is C++.

My guess they made an all-new Rust plugin which used an existing C++ library. Pretty common case when existing code base is slowly being converted to rust.

I guess the C++ library might be binary-only or difficult to compile but, for curious readers, you can definitely link C++ and Rust into a single binary library or exe

But how/why is libA failing if libB has already been initialized? That's the thing which seems broken.

But why are they dynamically linking to each other?