sortable 'tolerance' doesn't work as documented

The default for sortable is that tolerance is set to "intersect" which the documents say means "The item overlaps the other item by at least 50%." However, I can move an item and overlap it by 99% and it's still not moving the item to make room for the moved one. In my own application I'm able to do 100% and it seems to be random when it detects when to move the items around.

I'm using Google Chrome in Ubuntu and am seeing this issue on the demo page: http://jqueryui.com/sortable/

I wanted to include a screenshot but didn't know how to upload it so, here it is: http://imgbox.com/acxG9IoF You can see "Item 6" is nearly completely eclipsing "Item 5" but it's not moving.