Editmesh: Toggle between all edge-loop boundaries when selecting? Does anyone understand what Campbell means when he describes this new tool function?

https://developer.blender.org/rB276ef3b3b5192aad5c3e5e02c69246


  Description
  
  Editmesh: Toggle between all edge-loop boundaries when selecting
  
  Now Alt+RMB,RMB will select all connected boundaries.
  
  There are times when you just want to select an entire boundary loop
  ignoring face topology, previously there was no way to do this.


I've tried several models with different topology and Alt-RMB, RMB does not do anything beyond what I would expect.  I also tried releasing the Alt before clicking the second time but that does what we've always come to expect.

Well anyways, if someone has some thoughts on this matter, please shed some light.
It selects connected edge loops which are not connected to anything else (boundary edges):



This only affects cases where the loop is on the edge of a non-closed part of the mesh. For example, if you try this on an extruded grid (with thickness), nothing will happen as there are no boundary edges on a manifold mesh. 

It should also be noted that this doesn't seem to work with Shift.