Does 'max_worker_processes' include background process from postmaster?
I believe that they are two different processes and max_process_workers does not include the bg process. Both of them are set and defined separately. If you are talking about backgroud WOKER process (bgw) it is a complete different process and is not included in the max_process_workers by default as it has to be supplied in separate code by user and is surely maintained by postgres process itself.