winston logger includes handling uncaught promise rejections in exception handler

Question

I am learning a set of Node backend tools. I just added winston and winston-mongodb logging. I am hoping someone with more experience with winston can clarify whether the uncaught exceptional handler is assumed to also deal with unhandled promises. From the docs, I assumed these were designed as two separate, distinct handlers. In which case, I am rather stuck on a bug. I cannot find a way to separate out unhandled promise rejections from general uncaught exceptions. I can essentially create a more narrow, duplicate log for only unhandled promises. But those unhandled promises will be included with the uncaught exception logs. I spent some time logging the transports, but I could turn up any obvious reasons in the way I set up the transports for what seems like duplication. I am wondering at this point if this is expected behavior.

Thanks!