Deselect All does nothing when you edit width profile of selected path
If you have a path selected and you work on editing its width markers with a proper tool and then Deselect all — path get deselected, but you still have your width markers active.
So, AI basically allows you to edit width markers on paths without selecting them. It can be treated both good and bad, but when I say 'Deselect' I usually mean 'Stop anything from being selected' in ANY meaning, including editing width profile. Pressing Escape helps, but... you just don't expect it.