Indeed, dwarves can't move tasked items. This shows up most frequently when building a wall on top of a rock pile - easy, 0-1 distances....third of the wall/floor gets suspended because somebody else is building a wall 1 tile to the right.
Of course, the fact that this blocking is possible pretty much shows that quantum stockpiling, beyond being the native and only way to use either track stops or dump designations, could also be trivially blocked. This helped me realize that lot of stuff listed as exploit on wiki is just unintuitive to our earth physics, or just better than .40d era stuff.
(But as counterexample, contrast repeating spears and making stone blocks for skilling up an ability to legendary with repetitive tasks - then contrast infrastructure in making 5 tile irrigated farm plot and designating whole map for plant gathering.)
EDIT:
Apparently, a ruler doesn't get restored to their rightful position when returning to home from captivity.
Guess there's something to those "princess in hiding" stories, eh?
He then proceeded to take revenge on the humans in 10 years hence, killing 1828 people in a single winter siege.
An unknown creature then murdered the demon of treachery and strength next year.