> how erlang's shiny scheduler has an achilles heel when it comes to blocking C-based libraries.

It's an improvement but it was already possible to write C-based libraries. There are drivers, ports, NIFs were there before but for long running computation had to do your own thread and queue setup. This just avoids that bit because VM writers did it for the user so to speak (and probably did the right way).

Also it is really something advanced and not what most Erlang programmers would end up doing anyway. Once you start writing C code and directly loading it into the VM, the same caveats as before apply - that is a some fault tolerance and safety guarantees go out of the window.