I did not know about places, but after reading about them [1], I can see that although they are implemented on top of OS threads, it is not a conventional threading model.

For instance there is an instance of the Racket VM per place and this makes them heavier than it would be in a standard system programming language language such as C, C++ or Rust.

I am not saying it is better or worse -- just different.

[1] https://www.cs.utah.edu/plt/publications/dls11-tsffd.pdf