The problem isn't the propagation, it's the propagation by default. He wants errors that occur in development to pop a stack trace as soon as the error occurs without needing to attach a .catch handler.
Basically, implementations log the error to the console and raise the PotentiallyUnhandledRejection event if an error occurs inside a promise and no .catch handler was attached. If a .catch handler is attached _after_ the error is already logged, then a RejectionHandled event is raised. You can listen to those global events (the context is process in node, and window in browser, I think).
0: https://github.com/domenic/unhandled-rejections-browser-spec...