I agree this is somehow strange, as with other object or groups hiding the top thing is enough to make all content disappear.
Maybe someone will clarify this, who has more general vision and knowledge on how, why it ended up like that, and why not the other way.
Maybe it has something to do with Job object being a different thing that just all it contains. It used to matter if you clicked on the job or a single path when postprocessing.
It would be good to know if it is ok for everyone to have all of the contents of the job visible when the job is made visible, then if one wants to hide parts of it they can just be clicked and hidden. "Hide other paths" would be useful too. This would require the job not to display the code on its own as it is now. Another way would be "hide all" option in menu when right clicking on a Job.
I'm not sure where to look. It is possibly handed in FreeCAD general GUI part, but that is just my suspicion, and I don't know where is that. Some code could be in Path, and if there is a piece that reacts to Job's change in visibility it would be a very nice place to start. Enumerate the operations and hide them.