I think this rephrasing misses the mark a bit on the original concern. GP explicitly states that he wants Rust-the-language to remain as it is - close to the metal, no GC, with minimal runtime and 1:1 threading. The concern is indeed with the libraries/ecosystem. We are not quite there yet, but it is not hard to imagine that in a few years somebody who asks how to do some simple task in a blocking fashion will be met with replies in the vein of "well, that's not idiomatic", "why don't you use async", or "there was a library for that but it is now kind of unmaintained". All because the main effort of the community went into supporting and maintaining the async mode.

If the reqwest library indeed spawns a thread for every request, it is a good example of that dynamic. Sync mode kind of works but is clearly a second-class citizen and works in a suboptimal fashion. And if you want to peek under the hood to debug it you still have to deal with the async machinery in all its gory detail.