This is not about being able to filter an individual section, but to be able to use the ‘section’ value in a filter. This might seem strange but sometimes when we have a lot of items in a section we’d like to be able to make a view of just the tasks that are in a few specific sections, but then grouped in a different way that helps us float certain important-but-hiding tasks into view so they can be picked up.
We might for example want to see just the Doing, Up Next and Hold sections, and none of the backlog sections - and then show the items ordered by due date or another custom field.