Clarification on mouseenter/mouseleave

Hi gentlemen and ladies.

The specification for mouseenter and mouseleave
http://www.w3.org/TR/DOM-Level-3-Events/#event-type-mouseenter
http://www.w3.org/TR/DOM-Level-3-Events/#event-type-mouseleave
as far as I know, is the description of the first (and currently one and  
only) implementation of that same feature in any browser which is Internet  
Explorer.

a)
The spec however remarks that the event does not bubble. Well, in IE they  
do bubble. See attached testcase.

b)
The spec says "the propagation path must include the target element's  
child nodes as event targets". Is the spec implying that when the event is  
dispatched to the target, it's too dispatched to its children, therefore  
having many events being dispatched? Because that's really not what IE  
does.

Thank you.