TArray< TSubclassOf< UMoviePipelineSetting > > DefaultClasses
The settings specified here will automatically be added to a Movie Pipeline Master Configuration when using the UI. This does not apply to scripting and does not apply to runtime. It is only a convenience function so that when a job is created, it can be pre-filled with some settings to make the render functional out of the gate. It can also be used to automatically add your own setting to jobs.
This only applies to jobs created via the UI. If you do not use the UI (ie: Scripting/Python) you will need to add settings by hand for each job you create.