UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36

Steps to reproduce the problem:
1. For an example reproduction, visit https://developer.chrome.com/extensions/api_index
2. Open console and run the following code. 
document.addEventListener( 'mousemove', e => {
  console.log( e.path );
  console.log( document.elementsFromPoint( e.clientX, e.clientY ) );
})
3. Mouse over some of the table rows and td elements and observe that sometimes tr and tbody are present in the path but not present in the z stack returned by elementsFromPoint.
4. Use DevTools to highlight those elements and observe that they are in fact present, non-zero size, and are under the moused over elements.
5. Further observe they do not have any potentially interacting characteristics such as pointer-events: none

What is the expected behavior?
All elements in the z-stack should be returned under the point.

As per spec: https://drafts.csswg.org/cssom-view/#dom-document-elementfrompoint

What went wrong?
elementsFromPoint apparently fails to report some elements that the spec appears to require it to report.

Did this work before? N/A 

Chrome version: 53.0.2785.116  Channel: stable
OS Version: 10.0
Flash Version: Shockwave Flash 23.0 r0

Is this a spec bug or an implementation  bug?
Or is there some other behaviour which is not described by this bug report and everything is OK?