Usage considerations: Starting multiple processes at once when autoscale

Peter Lewis 

I have a question regarding this section in the documentation: https://docs.appian.com/suite/help/24.4/Start_Process_Smart_Service.html#starting-multiple-processes-at-once

Why do we need to implement this in two different ways, depending on whether autoscale is enabled or not? Can you give us some technical details? I would like to understand what is going on under the hood.