Adds links to 'All Drafts' and 'My Drafts' under the Posts, Pages, and other custom post type sections in the admin menu.
Does that post type have any drafts? By default, the plugin does NOT display the drafts links if no drafts are present for that post type. This behavior can be overridden (see the Filters section).
The "All Drafts" link is always hidden for users who are responsible for all drafts of a given post type, assuming the "My Drafts" link is configured to be displayed (which it is by default).
Like the Posts and Pages admin tables in WordPress, the default behavior of the plugin is to not show the drafts link if none are present for the post type since there isn't anything meaningful to link to. Bear in mind that the behavior can be overridden (see the Filters section).
Yes, which is why the plugin hides the "All Drafts" link when the "My Drafts" link is configured to be displayed (which it is by default) and the user is responsible for all of the drafts for a given post type.