I worked on some stepped airfoil research when I was in college as well. Had a professor that thought it would work especially well on unusually thick airfoils. Tested a step on an airfoil that must have been 35-40% thick. - Like a potato with a flap attached to the back end. The step behind the high point turned the flow considerably more than without the step. Not that it made it a practical airfoil though....
FWIW - There's nothing wrong with the use of the term "bound vortex" in this context. It happens to be widely applied as a virtual element in wing theory considerations, but that's not the only place it may be used. A web search on the phrase turns up it's application to real vortices on anything from airplanes to sailboats to swimmers' hands. The best definition I've found shows how broad the term really is - from an online fluid dynamics course from MIT:
The line vortex of figure 11.13 is called a bound vortex because it is held in a stationary position as the oncoming fluid flows around it. A bound vortex experiences a lift force given by equation 11.59. If the vortex is free to move with the fluid, i.e., has no velocity relative to the fluid surrounding it, then it experiences no lift force and is called a free vortex.
The only requirement for a vortex to be a bound vortex is that it is held in one place wrt the fluid flow. That is what we see in these step airfoils and on some sharp LE's.
I think that the reason sharp LE's are thought to hunt is again, vortices. I would bet that small bound vortices are continually forming and dispersing behind sharp leading edges at low angles of attack - which change the lift in an erratic fashion. I don't have anything to prove it, but that's the explanation I think is most likely for "hunting"
BTW - THat's a cool web site link to the step airfoils from Tatoo.
Thanks!