Probably some sort of flexibility / infectivity e.g. let’s say you have a function a which calls a function b with some borrowed data, b wants to spawn and return a thread (possibly wrapped in some other structure).

In the original acception I think you could literally do that, a scoped thread would just be a normal RAII object with various lifetime bounds.

With the new scoped threads, I’d think you need to create the scope in a and pass the scope handle to b so it can spawn the thread correctly.