I imagine this is optionally linked to the checkbox independence thing. Like there are times I want to make a checkbox item, and add some details that are not checkable things. But sometimes I want some to have checkboxes.
And if I check the root item, I don’t want all the boxes to get checkmarks. Unless, as you propose, the Cascade command is chosen.
Again, make checkable item is one thing. Cascade checkable is another thing.