If a user or group is only given the "deleterevision" the only thing that changes is they can see the checkboxes and the button for "change visibility". But if they check a box and hit the botton, the form for changing visibility gives them an error.
In other words, deleterevision alone is useless.
Since at least one WMF wiki wants deleterevision for a user group without the ability to undelete revisions (FA WP for its Eliminator group), this needs to be fixed.