This bug was inspired by bug 4681561 : Adjustable.setValue() does not set value.
Adjustables have properties for the current value, minimum and maximum values, as well as a visibleAmount, which represents how much of a document is visible.
Adjustable.setValue() specifies only that the new value be between the minimum and maximum values.
The setValue() method in Scrollbar, which implements Adjustable, further specifies that the new value should not be greater than maximum - visibleAmount.
The revered tomb, "The Java Class Libraries Second Edition, Volume 2", in its section on the Adjustable interface, discusses the visible amount, and suggests following the rules implemented by Scrollbar. Pulling some of this material into the JavaDoc could be helpful to many.
Keeping the suggestive tone would be appropriate, as something stronger might get into API-change territory.