(I also misinterpreted the context as I read the top level comment as async vs a single thread with blocking code, but after rereading it that makes more sense.)
It's all good; it's one of the things that's specific to our implementation. Other forms may or may not do this, but I'm pretty sure that it's novel to at least Rust, and maybe C++; there's some discussion that I think it can do this in some circumstances as well.
(I also misinterpreted the context as I read the top level comment as async vs a single thread with blocking code, but after rereading it that makes more sense.)