I assume this is unintended behavior.
Steps to reproduce:
1. Create an object.
2. Create 1, or more objects and make them children of the first object.
3. Look under appearance tab. Select hidden on the parent object, it hides all the children, as expected.
Leave it turned on.
4. Save the file, start a new map, then load the save.
5. Select the parent and toggle hidden, it only affects the parent and none of the children.
Not really a big deal, but if you accidentally save when a parent is hidden, and then reload later
You have to manually uncheck every child to able to see them again.