So I glossed over this thread when I first saw it, and something drew me back.

My first thought when reading the description is that it reminds me of the 'with' semantics you see for resource management, where the API gives you an resource that lives for the lifetime of the closure, and then is destroyed or returned to a pool.

That's is a refinement of RAII, where the API may initialize the connection or may allocate an existing one to you that is no longer in use (serial acquisition).

This feels like a refinement of that for thread lifetimes, which are probably not a bad thing.