Crate a ScrollPane with a TilePane full of rectangles. The height is calculated based on the min width of the tile pane not its width given current available width. End result is you end up with tons of extra space at bottom of ScrollPane.

You can see in the attached pic that all the content fits in the window but the scroll bar is showing and it's thumb is tiny indicating there is a lot more content to scroll but there is not, its all empty space.