I don't think that you understand what scrollsOnExpand is supposed to do.
First, your example does not does include a scroll pane. Second, your example
does not include multiple task panes, since only one task pane in a scroll pane
will have no effect, since it is already in the visible area.
Scrolls on expand is supposed to scroll a scroll pane to the display the
requested area. Therefore, when a task pane is expanded if the contents is not
completely visible, the scroll pane is supposed to respond by moving the task
pane to the top of the scroll pane (or at least far enough up to display the
entire contents if its smaller than the visible disaply area).
It sounds like you are seeing some kind of difference between isAnimated=true
task panes and isAnimated-false. Please confirm this is the case, but again
from your description of the problem and the provided test case, I do not see
how scrollsOnExpand is not working as expected.