So the execution model is now even more similar to Go's one, with the M:N scheduling, IIUC?

I much like to hear that, as I found Crystal to provide pretty much exactly the same concurrency primitives as Go, but with a much nicer syntax, as I compared here:

https://livesys.se/posts/crystal-concurrency-easier-syntax-t...

One big difference is that go hides all access to creating threads from the user, while execution contexts allow you to spin up dedicated thread(s) to solve a particular purpose.