Hm, I consider that a bug in WOverview (and there are many such bugs in the widgets where they don't treat left and right mouse buttons correctly in terms of their connections) -- it should be possible to left and right press it to get different functionality. 

Also, we hard-code emit-on-release too which shouldn't necessarily be the case (again, should be skin author choice as with other widgets) :-/. Oh the joy of old crufty code.